Truck axle weight calculator
A truck axle weight calculator shows how much of a load each axle group carries, so you can check a plan against legal limits before the truck is on the road. Enter the empty weight on each axle, where the cargo balances, and the cargo weight. The calculator splits the cargo between the axles by moment balance and compares steer, drive, trailer and gross weights with the limits for your region.
Two limit sets are built in and fully editable: US federal interstate limits and the Indian Ministry of Road Transport and Highways (MoRTH) maximum safe axle weights of 2018. It also shows the range of cargo positions that stays legal, how much more cargo fits, and a federal bridge formula calculator. It runs in your browser.
How to use the Truck Axle Weight Calculator
- Choose feet and pounds or metres and kilograms, the vehicle type and a limit set. Pick tandem or tridem for the drive and trailer axles.
- Enter the wheelbase and the empty weight carried by the steer and drive axles (from a scale ticket or the vehicle plate). For a semi-trailer, also enter the fifth wheel position, kingpin load and trailer axle load.
- Enter the cargo weight and the distance from the steer axle (or kingpin) to the cargo’s centre of gravity.
- Read each axle load against its limit, the legal range for the load position and the extra cargo you can still add.
Truck Axle Weight Calculator features
Moment balance
Cargo weight is split between axle groups by lever arm, and a semi-trailer passes its kingpin load on to the tractor.
US and Indian limits
Federal 20,000 / 34,000 / 80,000 lb and MoRTH 2018 axle norms as selectable sets, all editable.
Legal position range
Shows where the cargo centre can sit so every axle stays inside its limit.
Bridge formula
Computes 500 × (L·N ÷ (N − 1) + 12N + 36) for any axle group, rounded to the nearest 500 lb.
How the loads are worked out
For a rigid truck, take moments about the steer axle. The cargo’s share on the drive axles is cargo × x ÷ wheelbase, where x is the distance from the steer axle to the cargo’s centre of gravity; the rest goes to the steer axle. Eighteen thousand pounds centred 11 ft behind the steer axle of an 18 ft wheelbase puts 11,000 lb on the drive axles and 7,000 lb on the steer axle.
For a tractor and semi-trailer, the same step is done on the trailer: the trailer axles take cargo × x ÷ kingpin-to-axle distance and the rest goes to the kingpin. The kingpin load acts at the fifth wheel on the tractor, so it is split again between the steer and drive axles by its position. Weights are conserved: axle loads always add up to the empty weights plus the cargo.
The limits used
US figures are the federal interstate limits (20,000 lb single axle, 34,000 lb tandem, 80,000 lb gross) with the bridge formula; many states and permits differ, and non-interstate roads are set by states.
India: notification S.O. 3467(E) of 16 July 2018 raised the maximum safe axle weights to 3 t, 7.5 t and 11.5 t for single axles with one, two and four tyres, 21 t for tandem and 27 t for tri-axle, with GVW capped at 49 t (rigid) and 55 t (semi-articulated and truck-trailer), 1 t extra per axle with pneumatic suspension and a 5% GVW tolerance for enforcement. An amendment, S.O. 3881(E) of 6 August 2018, then modified it for some vehicles; widely reported effect is a 7 t two-tyre single axle, which this tool uses. Verify the gazette text and your vehicle’s approval; all limits are editable.
| Rule set | Single axle | Tandem | Tridem | Gross |
|---|---|---|---|---|
| US federal (23 CFR 658) | 20,000 lb | 34,000 lb | 42,000 lb (bridge formula, 8 ft) | 80,000 lb |
| India MoRTH 2018 | 7 t steer (two tyres), 11.5 t four tyres | 21 t | 27 t | 49 t rigid, 55 t semi-trailer; never above the sum of axle limits |
Limits of this calculator
- Axle groups are treated as one point at their centre, and the chassis as a rigid beam. Real loads shift with suspension, tyres, fuel and driver, so weigh the loaded vehicle where it matters.
- It does not model tyre load ratings, bridge-specific limits, axle spacing rules for individual groups, or minimum steer axle load.
- Limits change. Check the current federal, state or national rule and any permit before relying on a figure.
Truck Axle Weight Calculator FAQ
How do I calculate axle weight?
Take moments about an axle: the load on the other axle group is cargo × distance to cargo centre ÷ wheelbase. Add each share to the empty axle weights.
What is the federal bridge formula?
W = 500 × (L·N ÷ (N − 1) + 12N + 36), with L the feet between outer axles and N the axle count. W, rounded to the nearest 500 lb, is the most any axle group can carry; the 80,000 lb gross cap still applies.
What are the US axle weight limits?
Federal interstate limits are 20,000 lb on a single axle, 34,000 lb on a tandem and 80,000 lb gross, subject to the bridge formula. States can differ off the interstate.
What are the Indian axle load limits?
MoRTH’s 2018 norms allow up to 21 t on a tandem and 27 t on a tri-axle, with GVW of 49 t (rigid) or 55 t (semi-trailer). Check the gazette text and your vehicle’s type approval.
How do I fix an overloaded steer axle?
Move the cargo’s centre of gravity back towards the drive axles, or reduce the cargo weight. The range shown tells you how far.
Is it a substitute for a weighbridge?
No. It is a planning aid. A weighbridge reading governs for enforcement.