How do you calculate quarter-mile ET from horsepower and weight?

A common estimate is ET (seconds) = 5.825 × (weight ÷ HP)^(1/3), with trap speed MPH ≈ 234 × (HP ÷ weight)^(1/3). Weight should be race weight in pounds and HP the power you actually put down. These are rule-of-thumb formulas, not a guarantee of your next timeslip.

Is this crank horsepower or wheel horsepower?

Use the power number that matches how you race. Wheel HP usually predicts ET better for a street car; crank HP overstates performance if you ignore drivetrain loss. Whatever you enter, the math treats it as “effective” horsepower for the estimate.

Why does a lighter car go quicker at the same horsepower?

Power-to-weight is what moves you down the strip. Cutting pounds raises HP per pound, which shortens ET and raises trap speed in these formulas — the same reason racers obsess over weight reduction.

How accurate is a quarter-mile calculator?

It is a ballpark for comparing setups. Launch technique, traction, gearing, aero, altitude, and weather all move a real ET. Treat the result as a planning tool, then confirm at the track.

What weight should I enter?

Use race weight: vehicle + driver + fuel you will run with. Door-sticker curb weight alone is usually light. Convert kilograms to pounds (× 2.205) if your scale is metric — or use the kg toggle here.

Quarter Mile Calculator

Estimate 1/4-mile elapsed time and trap speed from race weight and horsepower — classic power-to-weight math for street and strip planning.

Estimate 1/4-mile ET and trap speed from weight and horsepower.

Race weight & power

Use race weight (car + driver + fuel) and the HP you expect to put down.

Weight (lb)

Horsepower (hp)

Drag strip · 1/4 mile

ET & trap from weight / power

Quick street estimate

Elapsed time

12.116

seconds

Trap speed

112.5

mph · 181 km/h

Tree → traps12.116 s

~60 ft
2.181
s (approx)
Power
400
hp
Weight
3600
lb

Power-to-weight: 0.111 hp/lb · Ballpark only — traction and gearing still matter at the track.

Quarter-mile ET from weight and horsepower

ET ≈ 5.825 × (weight ÷ HP)^(1/3) — a classic weight/power estimate.
Trap MPH ≈ 234 × (HP ÷ weight)^(1/3). Lighter or stronger cars trap higher.
Use race weight and realistic horsepower — these are planning numbers, not a timeslip.

Drag racers live and die by power-to-weight. This free quarter-mile calculator turns curb/race weight and horsepower into an estimated elapsed time and trap speed so you can compare a cam swap, a weight cut, or a turbo kit before you spend money — or brag online.

Enter race weight (car + driver + fuel) and the horsepower you expect to put down. The strip board shows ET, trap MPH, a rough 60-foot estimate, and hp per pound. Prefer wheel HP for street cars when you have it; crank HP without drivetrain loss will look optimistic.

Pair this with the horsepower calculator when you only have torque and RPM, and with gear ratio tools when you are dialing launch RPM and trap gear. Real ETs still need traction, weather, and a clean leave — confirm at the track.

Same 400 hp, three race weights

Power-to-weight moves the estimate more than people expect. These rows all use 400 hp and the classic cube-root ET / trap formulas. They are for comparing a diet to a cam, not for writing a timeslip before you have traction.

Quarter-mile estimate at 400 horsepower
Race weight	ET	Trap (approx.)
3,200 lb	11.65 s	117 mph
3,600 lb	12.12 s	112 mph
4,000 lb	12.55 s	109 mph

ET ≈ 5.825 × (lb ÷ HP)^(1/3); trap ≈ 234 × (HP ÷ lb)^(1/3). Wheel HP predicts a street car better than an optimistic crank number.

How to use the quarter-mile calculator

Enter race weight. Use curb weight plus driver and fuel — in pounds or kilograms.
Enter horsepower. Prefer wheel HP for a street car estimate, or crank HP if that is all you have. Switch to kW if needed.
Read ET and trap speed. Compare elapsed time, estimated trap MPH, and the rough 60-foot time before you change power or weight.

Quarter Mile Calculator

Quarter-mile ET from weight and horsepower

Same 400 hp, three race weights

How to use the quarter-mile calculator

Quarter-mile FAQ

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