Payload used
people + cargo/accessories + hitch hardware + tongue weightEvery pound carried by the tow vehicle is counted against the exact vehicle’s occupant-and-cargo capacity.
Method / revision 01
Every result should be traceable back to a number you can point at.
HitchMargin is a deterministic worksheet, not a vehicle-rating oracle. It calculates from values you enter, shows every check it performed, and names every important check still missing.
Open the calculatorFORMULASALL VALUES IN POUNDS
Payload margin
payload rating − payload usedA negative result is over the entered payload rating. A zero result has no remaining payload.
Tow-rating margin
maximum loaded trailer rating − loaded trailer weightLoaded trailer weight includes cargo, fluids, batteries, propane, and installed equipment—not brochure dry weight alone.
Tongue weight estimate
loaded trailer weight × entered tongue-weight percentageThe default control covers the common 10–15% conventional-trailer planning band. The exact manuals and measured weight control.
Gross combined margin
GCWR − (loaded tow vehicle weight + loaded trailer weight)The loaded vehicle should be weighed unhitched in the same trip-ready condition. Tongue weight remains part of total trailer weight and is not added twice.
Limiting factor
the entered check with the highest percentage of its rating usedHitchMargin compares relative headroom so a 100 lb tongue margin and 100 lb trailer margin are not treated as equally spacious.
What the result means
“Within” is not the same as “safe.”
Over a limit
At least one entered demand exceeds its entered rating. HitchMargin says not to tow the setup as entered.
Tight margin
At least one entered check has 10% or less rating headroom. That is a planning flag, not a legal or engineering threshold.
Within entered limits
No entered rating is exceeded. Missing checks, real loading, equipment condition, terrain, weather, and driving remain outside the result.
Source hierarchy
The exact label beats the generic brochure.
Use the vehicle’s driver-door Tire and Loading label for its occupant-and-cargo capacity. Use the certification label for GVWR and GAWR. Match the owner manual or OEM towing guide to the exact model year and configuration. Use the receiver’s own label for its weight-carrying or weight-distributing limits.
For actual weight, use a certified scale with the same passengers, cargo, fuel, hitch equipment, trailer cargo, water, propane, and batteries planned for the trip. If the loading changes, the report changes.
The federal tire-and-loading placard standard requires the combined occupant-and-cargo limit on applicable light vehicles. Manufacturer guidance also treats trailer tongue weight as load carried by the tow vehicle.
PRIMARY REFERENCESREVIEWED AUG 03, 2026
- 49 CFR § 571.110 — tire, loading, and occupant/cargo placard requirements
- Ford Towing and Trailering — weight definitions, labels, and current guide archive
- Ram Before You Buy — payload, tongue weight, and GCWR definitions
- SAE J2807_202411 — scope of tow-vehicle rating methodology
- NHTSA vPIC API — VIN decoding scope and endpoints
SAE J2807’s full technical text is not reproduced here. HitchMargin does not claim to recalculate or replace an OEM’s certified trailer rating.