GCWR Headroom Calculator

GCWR is the most the truck and trailer together may weigh. Find it in the owner's manual or manufacturer towing guide for your exact engine, axle ratio and cab/bed.

Formula

Headroom = GCWR − (loaded truck + loaded trailer). The best inputs come straight off a CAT scale ticket: the total of all axles with the trailer hooked up is your combined weight.

Safety note: These are planning estimates, not a guarantee your setup is safe or legal. Always verify with your truck's door-jamb sticker, the manufacturer's towing guide for your exact configuration, the trailer's VIN sticker, and a real weigh at a CAT scale. Never exceed any rating.

Last reviewed October 2026 by Jim Frith.