Fifth Wheel Pin Weight Calculator
US & CanadaPin weight is why a fifth wheel runs a truck out of payload long before its tow rating. Enter the trailer, the sticker and the hitch label and see which limit you hit first.
Fifth wheel pin weight and payload
Result
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Your rig, against every limit
Pin weight and the hitch both count in full against payload. They do not count again against GCWR: the truck carries what the trailer's axles no longer do. The pin band is maker guidance, not law.
The arithmetic
- Pin weight = loaded trailer weight × pin share (or weigh it)
- Payload used = people (150 lb each) + cargo + hitch hardware + pin weight
- Payload left = (GVWR − curb weight) − payload used
- Hitch: gross trailer rating over the trailer's GVWR, vertical rating over the pin weight
The default rig in the calculator is a 13,000 lb (5,897 kg) fifth wheel with a 13,995 lb (6,348 kg) GVWR, behind an illustrative three-quarter ton with 2,600 lb (1,179 kg) of payload on its sticker, two people, 200 lb (91 kg) of cargo and CURT's 171 lb (78 kg) sliding hitch. At 20% the pin is 2,600 lb (1,179 kg), and the truck is 671 lb (304 kg) over payload. Even at the 15% that Ford and Chevrolet use for their ratings, it is 21 lb (10 kg) over. The hitch, at 16,000 lb (7,257 kg) and 4,000 lb (1,814 kg), has room to spare. That is the usual shape of the answer: the hitch is rarely the problem, payload is.
Fifth wheel pin weight: how much is normal
Chevrolet's 2026 trailering guide: "For gooseneck/fifth-wheel trailering, the tongue weight should be 15% to 25% of the loaded trailer weight." Keystone, which builds the Montana, gives the same 15 to 25% in its owner's manual: "Keep the loaded tongue weight between 10% and 15% of the total weight for travel trailers and between 15% and 25% of total weight for fifth wheels." Both are manufacturer guidance, not law. We have not found a provincial or state statute that sets a pin weight percentage.
The number to watch is the low one. Ford's guide: "For 5th-wheel trailers, king pin weight is 15% of loaded trailer weight." Its maximum loaded trailer weight is worked out at that figure, and Chevrolet's guide says that when towing the maximum trailer weight the pin is 15%. Ram's towing pages put it at about 15% too. Real fifth wheels sit higher: the builders' own hitch weights in the table further down run 15 to 21.6% of the empty trailer. Every point above 15% is payload the brochure did not count.
| Loaded trailer | At 15% (rating figure) | At 20% | At 25% |
|---|---|---|---|
| 8,000 lb (3,629 kg) | 1,200 lb (544 kg) | 1,600 lb (726 kg) | 2,000 lb (907 kg) |
| 10,000 lb (4,536 kg) | 1,500 lb (680 kg) | 2,000 lb (907 kg) | 2,500 lb (1,134 kg) |
| 12,000 lb (5,443 kg) | 1,800 lb (816 kg) | 2,400 lb (1,089 kg) | 3,000 lb (1,361 kg) |
| 14,000 lb (6,350 kg) | 2,100 lb (953 kg) | 2,800 lb (1,270 kg) | 3,500 lb (1,588 kg) |
| 16,000 lb (7,257 kg) | 2,400 lb (1,089 kg) | 3,200 lb (1,451 kg) | 4,000 lb (1,814 kg) |
| 18,000 lb (8,165 kg) | 2,700 lb (1,225 kg) | 3,600 lb (1,633 kg) | 4,500 lb (2,041 kg) |
| 20,000 lb (9,072 kg) | 3,000 lb (1,361 kg) | 4,000 lb (1,814 kg) | 5,000 lb (2,268 kg) |
Pin weight too low is a loading problem, just as it is with a ball hitch: Ford says too little king pin weight can reduce rear-wheel traction and cause instability, and too much can press the truck down at the back until steering and braking suffer. Move load forward or back in the trailer, then weigh it again.
Gooseneck tongue weight
A gooseneck trailer's "tongue weight" is the same thing as a fifth wheel's pin weight, and the makers treat them as one. Chevrolet's 15 to 25% is written for "gooseneck/fifth-wheel trailering". Ram puts it at about 15% of the total load for a fifth-wheel or gooseneck trailer, and Ford's Super Duty pages say 15% for 5th-wheel and gooseneck towing. So the calculator above works for a gooseneck horse, livestock, flatbed or toy hauler trailer as it is: enter the loaded weight, the share or a measured figure, and the hitch's own ratings.
For comparison, a conventional ball hitch trailer runs 10 to 15%. That one has its own tongue weight calculator.
Why payload runs out before the fifth wheel tow rating
Three things the brochure figure leaves out, all of which ride in your truck:
- The pin above 15%. On a 14,000 lb (6,350 kg) fifth wheel, the step from 15% to 22% alone is 980 lb (445 kg).
- The hitch. Ram rates its trucks assuming 250 lb for a fifth wheel hitch. CURT's E16 slider weighs 171 lb.
- People and cargo. Ford's rating assumes a 150 lb driver and passenger and no cargo. Chevrolet says the weight of any additional equipment and all passengers other than the driver must be subtracted from payload to find the kingpin load available.
So the honest question is not "what can my truck tow" but "how heavy a trailer can my payload carry at this pin share". The calculator answers that in its last row. In the default rig it is 9,645 lb (4,375 kg) at 20%. The rear axle rating can also bind before GVWR does, because the pin sits just ahead of the rear axle and most of it lands there; Chevrolet and Ford both say the kingpin load must not take the truck over its rear GAWR. A scale with separate axle pads is the only way to check that. The payload calculator and Can I tow this? run the same arithmetic for a ball hitch.
Hitch weight and hitch rating
"Hitch weight" means two different things, and both matter here:
- The trailer's hitch weight, as RV builders print it, is the pin weight: Keystone defines it as the weight of the RV transferred to the tow vehicle's hitch. Grand Design's figure is for an empty standard build: "UVW and Hitch Weights are based on the average weight of the standard build."
- The hitch's own weight: the head, legs, rails or slider bolted in your bed. It is payload too. Ram assumes 250 lb for a fifth wheel hitch and 40 lb for a gooseneck when it rates its trucks.
A fifth wheel hitch carries two ratings: gross trailer weight and vertical load. CURT's E16 is rated 16,000 lb (7,257 kg) and 4,000 lb (1,814 kg). Keystone's rule for choosing one: "The hitch must be rated over the GVWR and the hitch weight of the RV." Sizing to the trailer's GVWR rather than its weight today leaves room for the day it is loaded to the plate. The calculator checks the hitch's trailer rating against the GVWR when you enter it.
How much does a fifth wheel camper weigh?
From the builders' own spec pages, the 19 fifth wheels below weigh 7,260 lb (3,293 kg) to 16,365 lb (7,423 kg) empty. RV builders sell these as fifth wheels; "gooseneck camper", "gooseneck RV" and "gooseneck travel trailer" describe the same shape, and Grand Design lists an insulated gooseneck among the Reflection's construction features. Empty weight is the floor: water, propane, food and gear come next, up to the GVWR on the trailer's plate.
| Model | Length | Empty (UVW) | Hitch weight | Hitch share | GVWR |
|---|---|---|---|---|---|
| Grand Design Reflection 100 22RK | 26' 11" | 7,260 lb (3,293 kg) | 1,180 lb (535 kg) | 16.3% | 9,995 lb (4,534 kg) |
| Grand Design Reflection 150 250ML | 28' 10" | 8,220 lb (3,729 kg) | 1,288 lb (584 kg) | 15.7% | 9,995 lb (4,534 kg) |
| Grand Design Reflection 150 260RD | 29' 10" | 8,280 lb (3,756 kg) | 1,319 lb (598 kg) | 15.9% | 9,995 lb (4,534 kg) |
| Grand Design Reflection 150 270BN | 29' 11" | 8,398 lb (3,809 kg) | 1,256 lb (570 kg) | 15% | 9,995 lb (4,534 kg) |
| Grand Design Reflection 100 24RL | 30' | 7,739 lb (3,510 kg) | 1,206 lb (547 kg) | 15.6% | 9,995 lb (4,534 kg) |
| Grand Design Reflection 100 28RL | 31' | 8,626 lb (3,913 kg) | 1,452 lb (659 kg) | 16.8% | 10,995 lb (4,987 kg) |
| Grand Design Reflection 100 27BH | 32' 3" | 8,315 lb (3,772 kg) | 1,331 lb (604 kg) | 16% | 10,195 lb (4,624 kg) |
| Grand Design Reflection 100 29RL | 32' 9" | 9,045 lb (4,103 kg) | 1,410 lb (640 kg) | 15.6% | 10,995 lb (4,987 kg) |
| Grand Design Reflection 303RLS | 32' 10" | 10,325 lb (4,683 kg) | 1,985 lb (900 kg) | 19.2% | 11,995 lb (5,441 kg) |
| Grand Design Reflection 150 295RL | 33' 9" | 9,577 lb (4,344 kg) | 1,570 lb (712 kg) | 16.4% | 10,995 lb (4,987 kg) |
| Grand Design Reflection 150 298BH | 34' 9" | 9,402 lb (4,265 kg) | 1,527 lb (693 kg) | 16.2% | 10,995 lb (4,987 kg) |
| Grand Design Reflection 337RLS | 35' 7" | 11,475 lb (5,205 kg) | 2,475 lb (1,123 kg) | 21.6% | 13,995 lb (6,348 kg) |
| Grand Design Reflection 100 32BH | 35' 11" | 9,570 lb (4,341 kg) | 1,480 lb (671 kg) | 15.5% | 11,995 lb (5,441 kg) |
| Grand Design Reflection 311BHS | 36' 11" | 11,700 lb (5,307 kg) | 2,450 lb (1,111 kg) | 20.9% | 13,995 lb (6,348 kg) |
| Grand Design Reflection 324MBS | 37' | 11,280 lb (5,117 kg) | 2,000 lb (907 kg) | 17.7% | 13,995 lb (6,348 kg) |
| Grand Design Reflection 360FLS | 39' 2" | 12,692 lb (5,757 kg) | 2,745 lb (1,245 kg) | 21.6% | 14,995 lb (6,802 kg) |
| Grand Design Reflection 362TBS | 39' 11" | 12,500 lb (5,670 kg) | 2,400 lb (1,089 kg) | 19.2% | 14,995 lb (6,802 kg) |
| Keystone Montana 3600RO | 40' 11" | 16,365 lb (7,423 kg)* | 3,410 lb (1,547 kg) | 20.8% | Not printed |
| Grand Design Reflection 367BHS | 41' 1" | 13,275 lb (6,021 kg) | 2,770 lb (1,256 kg) | 20.9% | 14,995 lb (6,802 kg) |
*Keystone prints a shipping weight, 16,365 lb (7,423 kg), and a carrying capacity, 3,045 lb (1,381 kg), for the Montana 3600RO rather than a UVW and GVWR. Hitch share is our arithmetic, hitch weight divided by empty weight, on the builders' empty figures. Brinkley's Model Z line, not in the table, prints hitch weights of 1,891 lb (858 kg) to 2,695 lb (1,222 kg) on UVWs of 10,691 lb (4,849 kg) to 14,997 lb (6,803 kg).
A 40 ft fifth wheel: the four in this sample from 39 ft 2 in to 41 ft 1 in run 12,500 lb (5,670 kg) to 16,365 lb (7,423 kg) empty. The 311BHS, at 36' 11", weighs 11,700 lb (5,307 kg) with a 2,450 lb (1,111 kg) hitch weight. For conventional travel trailers by length, see trailer weight by length.
Gooseneck vs fifth wheel
Both put the trailer's weight in the bed, near the rear axle. Chevrolet says these hitches place the kingpin weight near the truck's rear axle, must be attached to the frame, and must not use the bed for support. Ford says the hitch centre line should sit at least two inches ahead of the rear axle.
- Fifth wheel: a hitch plate mounted on rails in the bed that takes the trailer's kingpin. Ford: commonly used for RV trailers. CURT's fifth wheel hitches reach 30,000 lb (13,608 kg).
- Gooseneck: a ball in the bed. Ford: common for horse and agricultural trailers. CURT's gooseneck hitches reach 38,000 lb (17,237 kg); its 2-5/16 inch gooseneck ball #60616 is rated 30,000 lb (13,608 kg) and 7,500 lb (3,402 kg) vertical. Ball sizes are on the ball size page.
- Against a conventional hitch: the receiver tops out sooner. Ram's Class V receiver is limited to a 2,000 lb tongue on the 2500 and 2,300 lb on the 3500, and Ram requires a fifth wheel or gooseneck hitch above 20,000 lb (2500) and 23,000 lb (3500).
Factory prep makes the install simpler: Ford offers a factory 5th-wheel hitch prep package on Super Duty only, and Ram offers a Fifth-Wheel/Gooseneck Tow Prep Group on the 2500 and 3500 with factory provisions for both mounts. The hitch class finder covers receiver hitches.
Short-bed trucks: sliders and cab clearance
Ford is direct about it: "When selecting a trailer and tow vehicle, it’s critical that this combination provide clearance between the cab and tow vehicle for turns up to and including 90 degrees." It names the 5.5 and 6.5 ft F-150 boxes and the 6.75 ft Super Duty box as giving less clearance than a long box. Ram's advice is to consider a longer box for fifth wheel and gooseneck towing, for space to turn.
A sliding hitch is the usual fix. CURT's slider moves the coupling point 12 inches toward the rear so a short-bed truck can turn without obstruction, and CURT still says to check trailer-to-cab clearance for each truck and trailer. Whatever you use, try a slow 90 degree turn in an empty lot before the first trip.
Check the tailgate too. The trailer's nose has to clear it, and Ford prints the maximum closed tailgate height for that reason: 58.3 inches on the F-150 4x4, and 57.9 to 61.3 inches across the F-250 to F-450 and Tremor, depending on configuration and tires.
How to weigh your pin weight
- At a commercial scale, hitched: pull on until only the trailer's axles are on the scale, and record that.
- Unhook on the scale and record the whole trailer.
- Subtract: whole trailer minus axles is the pin weight. That is Keystone's method: "STEP 3: To determine hitch weight, subtract the axle weight from the total weight."
Ford's version is to put only the king pin on a scale at the height of the 5th-wheel king pin receiver. Weigh the trailer loaded for a real trip, with the fresh tank as you travel, then put the figure in the calculator's measured field. Weighing the truck's rear axle at the same visit checks the rear GAWR as well.
F-150, F-250, Ram 2500 and Silverado 2500 HD
People search by truck, so here is what we have read at source. F-150: Ford's guide carries a separate 5th-wheel/gooseneck towing table for it, and its short boxes are the ones Ford warns about for cab clearance. F-250 and Super Duty: factory 5th-wheel prep is offered on Super Duty only. Ram 2500: a fifth wheel or gooseneck hitch is required above 20,000 lb, and the Tow Prep Group adds factory mounts. Silverado 1500 and 2500 HD (and the GMC Sierra twins): Chevrolet's guide has separate gooseneck/5th-wheel rating tables for the 1500, 2500 HD and 3500 HD.
We are not printing per-truck ratings: they change with cab, bed, engine, axle ratio and model year, and the number that decides your answer is the payload on your own door sticker. Look up your configuration in the towing guide for your model year, then enter your sticker figures above. The VIN will not give you a tow rating; the VIN page explains why, and the door sticker page shows where each rating is printed.
Sources
- Chevrolet, 2026 Trailering Guide, Trailering basics, p. 8 (guidance, not law): Chevrolet's band for gooseneck and fifth wheel pin weight is 15 to 25 percent of the loaded trailer, against 10 to 15 percent for a conventional trailer. The same page says that when towing the maximum trailer weight, the maximum tongue weight is 10% for conventional trailers and 15% for gooseneck/fifth-wheel trailers, so the published rating is worked out at the bottom of the band. The Silverado 1500 gooseneck/5th-wheel kingpin notes on p. 28 repeat 15% to 25% and add that kingpin weight cannot take the truck over its rear GAWR or GVWR. Checked 2026-10-24.
- Chevrolet, 2026 Trailering Guide, Vehicles and hitches, p. 5 (guidance, not law): Gooseneck and fifth wheel hitches sit in the bed and place the kingpin weight near the truck's rear axle; the hitch must be attached to the truck frame, not supported by the bed. The weight of any additional equipment and all passengers other than the driver must be subtracted from the payload to find the maximum kingpin load available. The guide carries separate Silverado 1500 Gooseneck/5th-Wheel Trailer Weight Ratings (pp. 28 to 30) and Silverado 2500 HD and 3500 HD Conventional and Gooseneck/5th-Wheel Trailer Weight Ratings. Checked 2026-10-24.
- Ford, 2026 RV & Trailer Towing Guide, Maximum Loaded Trailer Weight and Measuring Tongue Load, PDF p. 7 (guidance, not law): Ford's Maximum Loaded Trailer Weight assumes a king pin weight of 15% for a 5th-wheel trailer, a 150 lb driver and passenger and no cargo, so options, passengers, cargo and the hitch must be deducted. Ford's worked example: an 11,500 lb 5th-wheel trailer times .15 is a 1,725 lb king pin weight. To weigh it on a commercial scale, put only the king pin on the scale, at 5th-wheel king pin receiver height. Too much king pin weight can press the truck down at the back until traction, steering response and braking suffer; too little can reduce rear-wheel traction and cause instability. The Super Duty pages (p. 20) say the king pin load and passengers and cargo must not take the truck over rear GAWR or GVWR. Checked 2026-10-24.
- Ford, 2026 RV & Trailer Towing Guide, 5th-Wheel and Gooseneck hitches, PDF p. 5 (guidance, not law): A 5th-wheel hitch mounts in the bed on rails and is commonly used for RV trailers; a gooseneck hitch puts the trailer weight over the truck's rear axle and is common on horse and agricultural trailers. Ford says the hitch centre line should be at least two inches forward of the rear axle. Shorter boxes (5.5 and 6.5 ft F-150, 6.75 ft F-250 and F-350) give less cab clearance than long boxes. Ford offers a factory 5th-wheel hitch prep package for Super Duty only. Checked 2026-10-24.
- Ford, 2026 RV & Trailer Towing Guide, Tailgate Clearance and frontal area, PDF pp. 18 and 21 (guidance, not law): Ford lists the maximum closed tailgate height a gooseneck or 5th-wheel trailer has to clear: F-150 4x4 58.3 inches (p. 18); F-250 SRW 57.9 to 60.0, F-350 SRW 57.9 to 59.7, F-350 DRW 58.0 to 59.7, F-450 DRW 58.6 to 60.3 and Tremor 59.5 to 61.3 inches, varying by configuration and tire size (p. 21). The F-150 has its own 5th-wheel/gooseneck towing table, separate from conventional towing, and Ford caps trailer frontal area at 75 sq ft for all 5th-wheel and gooseneck applications. Checked 2026-10-24.
- Ram, 2026 Ram Heavy Duty Payload & Towing Weight Capacities, footnote 10 (guidance, not law): The hitch weights Ram assumes under SAE J2807 when it rates the 2500 and 3500, along with 300 lb of passengers and 100 lb of options. For gooseneck and 5th-wheel trailers the tongue weight should never exceed manufacturer recommendations including payload and GAWR. A 5th-wheel or gooseneck hitch is required over 20,000 lb on the Ram 2500 and over 23,000 lb on the Ram 3500; the Class V receiver tongue limit is 2,000 lb (2500) and 2,300 lb (3500). The chart also describes the available Fifth-Wheel/Gooseneck Tow Prep Group with factory provisions for 5th-wheel and gooseneck mounts. Checked 2026-10-24.
- Ram, Towing: Before You Buy (guidance, not law): Ram puts tongue weight at roughly 10% for a conventional trailer and about 15% of the total load for a fifth-wheel or gooseneck trailer, and says payload plus tongue weight cannot exceed the payload capacity. Checked 2026-10-24.
- Keystone RV, 2026 Owner's Manual, Towing Considerations, p. 28, and Ramp RV Weight Distribution, p. 83 (guidance, not law): An RV builder's own band for fifth wheel pin weight, 15 to 25 percent of the loaded trailer, matching Chevrolet's. Keystone's example on p. 83: an 8,000 lb fifth wheel should have a pin weight of 1,200 to 2,000 lb. Keystone also recommends a tow vehicle with a tow rating of at least the RV's GVWR (p. 28), and defines hitch (tongue/pin) weight as the weight of the RV transferred to the tow vehicle's hitch when hooked up. Checked 2026-10-24.
- Keystone RV, 2026 Owner's Manual, Hitch Selection, p. 29 (guidance, not law): Size the fifth wheel hitch to the trailer's GVWR, not to what it weighs today, and to its hitch weight. Keystone does not supply the tow vehicle hitch. Checked 2026-10-24.
- Keystone RV, 2026 Owner's Manual, Weighing Your RV, p. 24 (guidance, not law): Keystone's scale method: pull on until only the RV's axles are on the scale and record that; unhook the RV on the scale for its total weight; the difference is the hitch weight, which is carried by the tow vehicle, not the RV's suspension. If the total is over the GVWR the RV is overloaded. Checked 2026-10-24.
- Grand Design RV, Reflection Fifth Wheels, Product Line Specifications: UVW, hitch weight, GVWR and length for seven Reflection fifth wheels, 32 ft 10 in to 41 ft 1 in, UVW 10,325 to 13,275 lb, hitch 1,985 to 2,770 lb, GVWR 11,995 to 14,995 lb. The page lists an insulated gooseneck among the construction features: the builder's own word for the raised front section of the fifth wheel. Checked 2026-10-24.
- Grand Design RV, Reflection 100 Series Fifth Wheels, Product Line Specifications: UVW, hitch weight, GVWR and length for six lighter Reflection 100 Series fifth wheels, 26 ft 11 in to 35 ft 11 in, UVW 7,260 to 9,570 lb, hitch 1,180 to 1,480 lb, GVWR 9,995 to 11,995 lb. Checked 2026-10-24.
- Grand Design RV, Reflection 150 Series Fifth Wheels, Product Line Specifications: UVW, hitch weight, GVWR and length for five Reflection 150 Series fifth wheels, 28 ft 10 in to 34 ft 9 in, UVW 8,220 to 9,577 lb, hitch 1,256 to 1,570 lb, GVWR 9,995 to 10,995 lb. Checked 2026-10-24.
- Grand Design RV, Reflection 311BHS spec sheet: Grand Design's UVW and hitch weight are for an empty standard build, not a loaded trailer: the 311BHS sheet gives UVW 11,700 lb and hitch weight 2,450 lb, matching the line page, with 74 gal fresh, 87 gal gray and 87 gal waste tanks. Checked 2026-10-24.
- Keystone RV, Montana 3600RO Luxury Fifth Wheel, specifications: A 40 ft 11 in luxury fifth wheel: shipping weight 16,365 lb, carrying capacity 3,045 lb, hitch 3,410 lb, 77 gal fresh water, two propane tanks. Keystone says website data reflects the most recent production run and to read the labels on the trailer for actual weights. Checked 2026-10-24.
- Brinkley RV, Model Z Fifth Wheels, Weights, Dimensions and Capacities: Seventeen Model Z floorplans (2670 to 3610): UVW 10,691 to 14,997 lb, GVWR 13,995 to 17,995 lb, hitch 1,891 lb (2670, UVW 10,691 lb) to 2,695 lb (3510, UVW 14,815 lb). Checked 2026-10-24.
- CURT, E16 Sliding 5th Wheel Hitch, 16,000 lbs. #16511 (guidance, not law): A real fifth wheel hitch's two ratings and its own weight: 16,000 lb gross trailer weight, 4,000 lb vertical load, product weight 171 lb. Its S20 slider moves the coupling point 12 inches toward the rear so a short-bed truck can turn without obstruction; CURT still says to ensure adequate trailer-to-cab clearance for each truck-trailer configuration. Tested in accordance with SAE J2638. Checked 2026-10-24.
- CURT Manufacturing, Types of Trailer Hitches and Hitch Classes, Types of Trailer Hitches (guidance, not law): Capacity ranges CURT gives for its own hitch types: receiver hitch up to 20,000 lb, 5th wheel hitch up to 30,000 lb (pickup trucks only, couples to a kingpin), gooseneck hitch up to 38,000 lb (pickup trucks only, a ball in the truck bed), pintle hitch up to 60,000 lb (hook and lunette ring, heavy-duty vehicles). A bumper hitch's capacity is limited to the bumper. Checked 2026-10-24.
- CURT, Double Lock 2-5/16" Gooseneck Ball #60616 (guidance, not law): A 2-5/16 inch diameter gooseneck ball that CURT says couples to most gooseneck trailers, rated 30,000 lb GTW and 7,500 lb vertical load. Checked 2026-10-24.
- 49 CFR 567.4(g)(3): The 150 lb per seat this site uses for occupants is the figure the regulation itself builds GVWR from. It is not a guess, and it is not an average adult. Checked 2026-10-23.
Every pin weight, payload and percentage in the tables is arithmetic from the sources above or from the calculator's engine.