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Automotive Calculators

Quarter-Mile Calculator

2026-09-27 6 min

Predict quarter-mile ET and trap speed from weight and power with the proven Hale formulas.

Elapsed Time
13.21 s
Quarter-mile ET
Trap Speed
103.2 mph
Speed at the stripe

Calculator

Race Weight(lb) Help
lb

Car + driver + fuel

Wheel Horsepower(whp)
whp
Results update live as you type

Live statistics

Elapsed Time

13.21 s

Quarter-mile ET

Trap Speed

103.2 mph

Speed at the stripe

Results

Optimal

Elapsed Time

13.21s

Quarter-mile ET

Trap Speed

103.2mph

Speed at the stripe

Planning estimate from standard automotive formulas. Validate with dyno, timeslip or datalog data when precision matters.

Visualizations

Results overview

13.2Elapsed Time
103.2Trap Speed

Elapsed Time vs. Race Weight

Elapsed Time

13.2s
820

Formula

Hale’s empirically fitted quarter-mile relations — power-to-weight to the one-third power, calibrated on thousands of timeslips.

ET = 5.825 × (W ÷ HP)⅓ · Trap = 234 × (HP ÷ W)⅓

Variables

SymbolNameUnitDescription
WRace weightlbWith driver
HPWheel powerwhpAverage-effective WHP

Explanation

Cube-root scaling: doubling power cuts ET by only ~21% but raises trap ~26% — why trap reflects power and ET reflects launch.

Step-by-Step Calculation

Follow each step to understand how the result is calculated from your inputs.

Step 1

Record the inputs.

Race Weight:3500 lb
Wheel Horsepower:300 whp
Result: 2 inputs ready
Step 2

Apply the formula.

ET = 5.825 × (W ÷ HP)⅓ · Trap = 234 × (HP ÷ W)⅓
Result: Primary result = 13.21 s
Step 3

Read every derived output.

Elapsed Time:13.21 s
Trap Speed:103.2 mph
Result: Elapsed Time = 13.21 s
Final Answer
13.21

Worked Examples

See how the calculator works with different scenarios.

Scenario

3,500 lb, 300 whp.

Inputs

Weight:3,500 lb
Power:300 whp

Calculation

ET = 5.825 × (11.67)⅓ = 13.20; trap = 234 × (0.0857)⅓ = 103.1

Result

13.20 s @ 103.1 mph.

Interpretation

Textbook bolt-on V8 timeslip.

Understanding Your Result

Your Result: Elapsed Time: 13.21 s

Typical range: 14s family cars · 13s sporty · 12s fast street · 11s and under: serious.

What This Means

Your likely timeslip from power and weight alone.

Why It Matters

The universal bench-racing currency — and the dial-in starting point.

Professional Interpretation

Treat the primary result as a planning estimate, then validate on a dyno, at the track, or with logged sensor data. If measured numbers disagree by more than ~10%, re-check inputs (units are the usual culprit) before changing parts.

Recommendations

  • •Double-check units on every input before trusting the result
  • •Compare against the worked example below to sanity-check magnitude
  • •Validate with measured data (dyno, timeslip, datalog) when it matters

Learn — fuel economy, deeply

The quarter mile compresses the whole car — power, weight, gears, grip — into two numbers.

1 · Where the gallon goes (energy path)

Engine heat

60–70% lost

Coolant + exhaust carry most energy away. Hybrids recover some via Atkinson cycle + regen.

Driveline

5–15% lost

Transmission, differential, accessories. CVTs and 8–10 speed autos lose less.

Aero drag

∝ v²

Doubles from 55→78 mph. Roof boxes hurt more than trunks.

Rolling + brakes

10–20%

Tires, weight, stops. Regen braking (hybrid/EV) reclaims city braking energy.

4 · Measure like a pro (the 3-tank protocol)

  1. Fill to first click at the same pump, record the odometer (Tank 0).
  2. Drive normally for 2–3 tanks; always refill to first click at the same pump.
  3. MPG = total miles ÷ total gallons across all tanks — averaging kills pump-click noise.
  4. Cross-check with the trip computer; a persistent >10% gap means the computer needs calibration — or the car needs service.
  5. Log with an OBD-II dongle for per-trip MPG if you want to isolate commute vs. highway behavior.

Practical Tips

  • •Start from the default values — they describe a typical combination
  • •Use the sensitivity chart to see which input moves the result most
  • •Keep units consistent (all inches or all mm, never mixed)

Common Mistakes

Mixing units (inches with mm, psi with kPa)
Convert every input to the unit shown on its field before calculating.
Trusting a single output blindly
Cross-check with the worked example and, when it matters, a dyno or datalog.

Assumptions

This calculator makes the following assumptions to provide estimates:

Steady-state model: Formulas assume stabilized conditions; transients, heat soak and traction limits are excluded.
Standard factors: Empirical constants (BSFC, VE, drivetrain loss) use typical values — your combination may differ.

Limitations

Be aware of these limitations when using this calculator:

Estimate, not measurement: Predictions carry real-world scatter of roughly ±5–15% depending on the model.
No transient effects: Shift time, wheelspin, spool lag and heat soak are not modeled here.

Frequently Asked Questions

Answers to common questions about this calculator.

ET or trap — which shows power?
Trap speed. ET is dominated by launch and traction; trap reflects power-to-weight.
Use crank or wheel HP?
Wheel HP. Crank figures flatter ET by ~0.5 s and trap by ~5 mph.
How accurate?
Typically ±0.3 s / ±3 mph for sorted street cars on decent tires.

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Related Guides

Deepen your understanding with these educational resources.

Glossary

Technical terms used in mortgage calculations explained in plain language.

MPG
Miles per gallon. Distance travelled per gallon of fuel; higher is better. US gallon = 3.785 L.
L/100 km
Litres consumed per 100 kilometres; lower is better. Standard metric efficiency unit.
MPGe
Miles per gallon-equivalent. EV metric: miles travelled on 33.7 kWh (energy of 1 gal of gasoline).
CAFE
Corporate Average Fuel Economy — US fleet-average efficiency standard enforced by NHTSA.
Rolling resistance
Energy lost deforming tires as they roll. Low-pressure or wide tires raise it.
Aerodynamic drag
Air resistance growing with the square of speed — why highway MPG falls fast above 60 mph.
Hypermiling
Driving techniques (coasting, steady speed, anticipation) that maximise real-world MPG.
OBD-II
On-board diagnostics port. Scanners and dongles read live MPG, fuel trim and fault codes.

Authoritative References

Trusted sources and standards referenced by this calculator.

Applicable Standards

EPA Fuel Economy Testing (40 CFR Part 600)CAFE — Corporate Average Fuel Economy Standards (NHTSA)WLTP — Worldwide Harmonised Light Vehicle Test ProcedureSAE J1321 / J1711 — Fuel consumption test proceduresISO 2575 — Road vehicles symbols & efficiency markings

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