Elevator rated load and capacity calculator

Minimum rated load from the car's inside platform area, or the largest car area a rated load allows, by the ASME A17.1/CSA B44 passenger formula, with the EN 81-20 person count.

Still needs a trade check. Treat each point below as unconfirmed, not as code, until it is checked against a licensed copy of the cited edition:

The two pound and square foot formulas were confirmed in the public text of A17.1-2016 (8.2.1.1 and 8.2.1.2, which 2.16.1.1 points to); the 2019 edition cited here still needs a trade check.
A17.1 also prints the formulas in kilograms and square metres, which give a slightly lower load than converting the pound result; this calculator converts the pound result, so it never reads below either.
The EN 81-20 rule of 75 kg per person, rounded down, was found only in public summaries; its subclause and its area table cap still need a trade check.

Link to these inputs Opening or sharing this link puts your inputs in a URL sent to the server, which may remain in browser history and request logs.

Result

Rated load: 3,281 lb
Inside net platform area: 36.11 ft²
Persons (EN 81-20, 75 kg each): 19

Not engineering advice; a licensed professional checks every result. Not a substitute for a licensed engineer, the manufacturer's data or the authority having jurisdiction; confirm the code edition your jurisdiction has adopted. First build: the code limits used here await a trade check against a licensed copy of the cited edition. Terms of use and estimate disclaimer.

Drawing

Car plan with its inside area.

Working

Inside net platform area
$A = w \times d$
A = 2.032 m × 1.651 m = 3.354832 m² = 36.1111111111111 ft²
= ≈ 36.1111 ft²
Minimum rated load (area up to 50 ft²)
$W = 0.667A^2 + 66.7A$
W = 0.667 × 36.1111111111111² + 66.7 × 36.1111111111111 ≈ 3278.387 lb ≈ 1487.051 kg
= 1488 kg, the minimum rounded up to a whole kilogram (3281 lb, rounded up from that rating)
Persons by EN 81-20's 75 kg rule (from the rated load returned)
$n = \left\lfloor Q \div 75 \right\rfloor$
n = ⌊1488 kg ÷ 75 kg⌋ = 19
= 19 persons

Working is shown in the units each formula is written in; the result figures above follow the unit switch. A numeric input is taken to 15 significant digits before it is used (1033.2293579541322 kg is used as 1033.22935795413 kg); every echo of it shows that value, and a computed figure substituted into the working is quoted to 15 significant digits as well.

Notes

A rated load at or above this value satisfies the area rule for this car; a lower rated load would need a smaller car.
ASME A17.1 rates a passenger car by load, not by persons. The person count shown uses EN 81-20's 75 kg rule only; EN 81-20 also caps persons and load by car area through its own tables, which this build does not apply.
Inside net platform area is taken as inside width times inside depth; a car with recesses or a non-rectangular floor needs the area measured to the code's definition.

Method

What the rule does

A passenger elevator must be rated for at least a minimum load that grows with the floor area inside the car, so that a car cannot be crowded with more people than its machine, ropes and safeties are designed to carry. ASME A17.1/CSA B44 states this as a formula in pounds and square feet with one curve for cars up to 50 square feet and a second curve from there up to 230 square feet.

This calculator runs the formula in both directions. From a car's inside width and depth it gives the lowest rated load the car may carry. From a rated load it solves the same formula for area, giving the largest inside net platform area that rating allows.

How the numbers are worked

The area is the inside width times the inside depth, converted to square feet. For an area A up to 50 square feet the minimum rated load W in pounds is 0.667 times A squared plus 66.7 times A. Above 50 square feet it is 0.0467 times A squared plus 125 times A, minus 1367. At 50 square feet the two curves come close but do not meet: the first gives 5,002.5 pounds and the second 4,999.75 pounds.

Going the other way, each curve is a quadratic in A, so each has one positive root. A root counts only if it falls in its own curve's range. The two curves do not meet exactly at 50 square feet, so for loads between about 4,999.75 and 5,002.5 pounds both roots count, and the calculator gives the larger area. That exact root is then rounded down, to 0.01 square foot or 0.001 square metre, and checked forward, so the area shown never needs more than the rated load; the drawing is labelled with that same figure and its side lengths are rounded down too.

The person count uses the EN 81-20 rule of one passenger per 75 kg of rated load, rounded down. EN 81-20 also limits the load and the persons by car area using tables of its own; those tables are not applied in this build.

Limits of this calculator

It covers passenger elevators only. Freight classes, limited-use elevators and private residence elevators follow other rules. Areas above 230 square feet are outside its range.

Formulas

Area up to 50 ft²

W = 0.667 A^2 + 66.7 A (W in lb, A in ft², A <= 50)

W = 0.667A^2 + 66.7A

Area above 50 ft² to 230 ft²

W = 0.0467 A^2 + 125 A - 1367 (W in lb, A in ft², 50 < A <= 230)

W = 0.0467A^2 + 125A - 1367

Persons (EN 81-20)

n = floor(Q / 75) (Q in kg)

n = \left\lfloor Q \div 75 \right\rfloor

Code basis: clause and edition

Standard	Edition	Clause	What it covers
ASME A17.1/CSA B44	2019	2.16.1.1, with the formulas of 8.2.1.1 and 8.2.1.2	Minimum rated load for passenger elevators from inside net platform area
EN 81-20	2020	5.4.2	Rated load and number of passengers (75 kg per person)

Rules are restated in our own words and computed for your inputs; no table or text from a standard is reproduced. The adopted edition varies by jurisdiction, so confirm the one your authority having jurisdiction enforces.

Inputs

Input	Unit	Range	Default
Work out `direction`	choice	area-to-load, load-to-area	area-to-load
Car inside width `carWidth`	millimetres (mm)	600 to 5000	2032
Car inside depth `carDepth`	millimetres (mm)	600 to 5000	1651
Rated load `ratedLoad`	kilograms (kg)	100 to 13500	1587.573295

Worked examples

Each example below is a test the calculator must pass before it ships. The expected values were worked out by a separate implementation.

Example	Expected result (each in its declared unit)
A 2032 mm by 1650 mm car (80 in by just under 65 in, about 36 ft²)	area: 3.353 m², ratedLoad: 1486 kg, ratedLoadLb: 3277 lb, persons: 19
A 3,500 lb (1,588 kg) rated load	area: 3.532 m², areaFt2: 38.02 ft², ratedLoad: 1588 kg, ratedLoadLb: 3500.941 lb, persons: 21
A large car above 50 ft²: 2.5 m by 2.4 m	area: 6 m², ratedLoad: 3131 kg, ratedLoadLb: 6903 lb, persons: 41
Just below the break: 2,200 kg (small-car curve only)	area: 4.538 m², areaFt2: 48.85 ft², ratedLoad: 2200 kg, ratedLoadLb: 4850.17 lb, persons: 29
At the break: 2,268 kg. The exact larger root is a large-car area just over 50 ft², but rounding it gives an area under 50 ft² that needs more load, so the shown value steps down to the small-car root	area: 4.643 m², areaFt2: 49.98 ft², ratedLoad: 2268 kg, ratedLoadLb: 5000.084 lb, persons: 30
Just over the break: 2,269.2 kg (the rounded large-car area stays above 50 ft²)	area: 4.647 m², areaFt2: 50.02 ft², ratedLoad: 2269.2 kg, ratedLoadLb: 5002.73 lb, persons: 30
Just above the break: 2,300 kg (large-car curve only)	area: 4.695 m², areaFt2: 50.54 ft², ratedLoad: 2300 kg, ratedLoadLb: 5070.632 lb, persons: 30

For AI agents

This calculator is also the MCP tool elevator_rated_load at https://elevatorcalc.com/api/mcp, using the same function as this page. See how to connect, the llms.txt file, or the JSON catalogue.