01What this calculator tells you
This calculator checks how the weight of a tiny house build is actually carried by its trailer — not just whether the total is under some single number. Enter your cargo/build weight, the trailer’s own weight, how many axles it has, each axle’s rated capacity, the trailer’s GVWR, and your tow vehicle’s rated towing capacity.
You get the Gross Trailer Weight (GTW), the target tongue weight range, the load carried by each axle, and a pass/near-limit/over-capacity readout comparing that load against your axle rating, your trailer’s GVWR, and your tow vehicle’s towing capacity. The Federal Motor Carrier Safety Administration and state DMVs treat these ratings as hard limits, not suggestions.
02Load status categories
The result compares your numbers against the worst-case percentage across axle load, GVWR, and tow capacity, and reports one of three statuses.
This is a planning and sanity-check calculator, not a substitute for weighing your actual trailer or a licensed engineer’s sign-off on a custom build.
- Estimated inputs only. The result is only as accurate as the weights you enter — confirm your real numbers on a certified scale before your first long tow.
- Tongue weight target is a rule of thumb. The 10-15% band is widely used, but your trailer manufacturer’s specific recommendation always takes precedence.
- Frame strength matters too. Upgrading axles alone does not make an overloaded trailer safe if the frame was not designed for the added weight.
- State rules vary. Registration, titling, and brake requirements for homemade or converted trailers differ by state — check with your state motor vehicle agency (for example New York’s DMV trailer registration rules) before the road.
- Federal safety standards apply to the trailer itself. A compliant trailer must meet Federal Motor Vehicle Safety Standards; NHTSA has warned buyers that noncompliant trailers sold as sheds or utility units on wheels can be unsafe to tow.
- Not a substitute for cargo securement rules. How the load is distributed and tied down inside the trailer matters as much as the raw totals.
- Select the number of axles your trailer has.
- Enter your total cargo/build weight — framing, siding, insulation, appliances, furniture, and belongings.
- Enter the trailer’s empty weight from its spec sheet or a certified scale.
- Enter the rated capacity of one axle (GAWR) and the trailer’s GVWR from its VIN/rating label.
- Enter your tow vehicle’s rated towing capacity from its owner’s manual or door-jamb sticker, then press Calculate.
The readout shows Gross Trailer Weight, the target tongue weight range, per-axle load, and how much margin you have on axle rating, GVWR, and tow capacity. Planning the build itself first? Check your conduit fill before locking in wall cavities, and browse more tools on the calculator home page.
03Related calculators
Working through a related project? Try our Tiny House Material Cost Calculator, Tiny House Off-Grid Solar Calculator, and Container Home Cost Calculator.
01The formula
The trailer load calculation chains four checks together: total weight, how much of it sits on the hitch, how much each axle carries, and whether every rated limit still has room. The National Highway Traffic Safety Administration has long advised relating a trailer’s tongue weight to the tow vehicle’s axle ratings for exactly this reason.
Where:
- GTW= Gross Trailer Weight — the trailer plus everything loaded onto it.
- GAWR= Gross Axle Weight Rating, the manufacturer’s limit for one axle.
- GVWR= Gross Vehicle Weight Rating, the trailer’s overall rated maximum.
02Worked example
Take a 3,000 lb empty trailer carrying a 7,000 lb build on two axles rated 5,200 lb each, a 10,400 lb GVWR, and a tow vehicle rated for 12,000 lb:
That last step is the point of checking all three ratings separately: the axle and tow-vehicle numbers look comfortable, but GVWR is close enough that a few extra cabinets or a full water tank could push the trailer over its rated limit.