Gross Combination Weight Check
Whether a tractor-trailer is within its weight limits.
Example
You enter
- Rated GCWR (lb) 80000
- Power-unit weight, loaded (lb) 18000
- Trailer weight, loaded (lb) 60000
- Federal gross cap (lb) 80000
You get
- Combined weight 78,000 lb
- GCWR margin 2,000 lb
- Federal margin 2,000 lb
- Within both limits Yes
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
ScopeThe combined power-unit plus trailer weight checked against both the manufacturer's rated GCWR and the federal 80,000 lb gross cap (editable), reporting each margin and the binding limit. Axle and bridge-formula limits are separate checks; a permit or the AHJ governs an over-limit move.
Formula or tablecombined = tractor + trailer; the binding limit is min(GCWR, federal_max); ok if combined <= binding, else over by combined - binding. GCWR margin and federal margin are reported separately.
Source and edition23 CFR 658.17 (80,000 lb federal gross) by section, with the manufacturer's GCWR rating plate; limits not reproduced.
Free accessRead-only at ecfr.gov. State limits may be lower than federal; a permit or the AHJ governs an over-limit move.
What governsMath aid for personal verification. The ELD on the truck and the carrier tariff are the legal record. State limits may be lower than federal.
API field namesgcwr_lb, tractor_weight_lb, trailer_weight_lb, federal_max_lb, combined_lb, margin_gcwr, margin_fed, ok
- Binding limit the smaller of the rated GCWR (structural / drivetrain) and the federal gross cap governs23 CFR 658.17
- Federal cap editable default 80,000 lb; edit for a state or permit limit23 CFR 658.17
- Separate checks axle limits and the federal bridge formula are separate checks, not covered here23 CFR 658.17