How to Use the Vehicle Weight Fuel Economy Calculator
Every pound you carry costs you at the gas pump. The US Department of Energy estimates that each 100 lbs of extra weight reduces fuel economy by roughly 1–2%. This calculator uses 1% per 100 lbs as a conservative baseline. Enter your unloaded MPG, how much extra weight you're carrying, and your annual mileage to see the real annual dollar impact of hauling cargo or passengers.
The biggest surprises often come from accumulated trunk junk — golf clubs, sports equipment, tools, and emergency supplies can easily add 50–150 lbs you forget is there. A roof rack alone adds aerodynamic drag on top of the weight penalty, so the actual loss for roof-mounted cargo is higher than this calculator shows.
Frequently Asked Questions
It's a reasonable average. Lighter vehicles (compact cars) typically see a 1.5–2% drop per 100 lbs, while heavier trucks and SUVs may only see 0.5–1%. This calculator uses 1% as a middle estimate applicable to most passenger vehicles.
Yes — heavier EVs consume more kWh per mile. The percentage impact is similar to gas vehicles, though regenerative braking recovers some energy on deceleration, partially offsetting the loss. The net effect is typically slightly less than in a comparable gas vehicle.