TowingMath

Trailer Axle Weight Calculator

Work out how much load each trailer axle carries, and whether that is inside its rating.

Your numbers

The whole trailer as it travels, including the tongue.
Carried by the tow vehicle, so it comes off the axles.
Stamped on the axle tube or listed on the VIN plate.
The lowest-rated component governs, and it is often the tires.
Load per axle —

Enter your numbers above.

Verify before you tow. These figures are a planning aid, not professional or engineering advice. Your real limits are the ones printed on your vehicle's door-jamb placard, your trailer's VIN plate, and your owner's manual - and those override anything calculated here. When numbers are close, weigh the rig and go with the more conservative answer.

The formula

Weight on axles = Loaded trailer weight - Tongue weight

Load per axle   = Weight on axles / Number of axles

Effective limit per axle = the LOWER of:
    axle GAWR
    tire rating x tires per axle (2 on a standard axle)

Worked example

A 7,000 lb tandem-axle trailer with 910 lb on the tongue (13%), on 3,500 lb axles riding on tires rated 1,820 lb each: 

Weight on axles = 7,000 - 910 = 6,090 lb
Load per axle   = 6,090 / 2   = 3,045 lb

Axle GAWR                   = 3,500 lb
Tire limit (1,820 x 2)      = 3,640 lb
Effective limit             = 3,500 lb  (the axle)

3,045 of 3,500 = 87% of rating. Inside, with 455 lb spare.

87% is workable but not generous. Because a tandem rarely splits load perfectly evenly, the heavier axle in practice could be carrying meaningfully more than 3,045 lb. At this margin it is worth weighing rather than assuming.

Need the ratings themselves? The trailer axle weight chart lists common capacities, what a bare axle weighs, and how to identify the axle you have.

Common questions

How do I calculate trailer weight per axle?

Subtract tongue weight from the trailer's loaded weight, then divide what remains by the number of axles. The tongue is carried by the tow vehicle, so it never sits on the trailer's own axles.

An even split is an estimate, not a measurement. Real trailers load their axles unevenly depending on where the cargo sits relative to the suspension, and on a tandem the front axle often carries more.

How much weight can a trailer axle carry?

The axle's GAWR is stamped on the axle tube or listed on the trailer's VIN plate, and that is the only figure that governs. Common trailer axle ratings are 3,500, 5,200, 6,000, 7,000 and 8,000 lb.

Important: the axle is only one link. Tires, wheels, springs and hubs each have their own rating, and the lowest one in that chain is your real limit. A 7,000 lb axle on tires rated for 2,800 lb each gives you 5,600 lb, not 7,000.

Do both axles on a tandem carry the same weight?

Rarely exactly. Equalizers are designed to share load between axles, but suspension wear, tire pressure differences, uneven cargo placement and a trailer that does not sit level all shift the balance.

Because of that, treat an even split as a planning figure and leave margin. If the calculated per-axle load is within a few hundred pounds of GAWR, weigh the trailer rather than assuming.

What if I am over the axle rating?

Remove weight. Overloaded trailer axles are a common cause of bearing failure, spring failure and blowouts, and those failures happen at highway speed with a loaded trailer behind you.

Upgrading axles is possible but it does not raise the trailer's GVWR - the frame, coupler, tires and brakes were all rated as a system, and the VIN plate figure still governs legally.

Related tools

Sources