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Performance Comparison Calculator

2026-09-27 6 min

Head-to-head: two cars’ power-to-weight, predicted ET and trap side by side with deltas.

Car A ET
12.00 s
Car B ET
12.18 s
ET Gap (A−B)
-0.18 s
Negative means A wins
Trap Gap (A−B)
1.7 mph

Calculator

Car A Power(whp)
whp
Car A Weight(lb)
lb
Car B Power(whp)
whp
Car B Weight(lb)
lb
Results update live as you type

Live statistics

Car A ET

12.00 s

Car B ET

12.18 s

ET Gap (A−B)

-0.18 s

Negative means A wins

Trap Gap (A−B)

1.7 mph

Results

Optimal

Car A ET

12.00s

Car B ET

12.18s

ET Gap (A−B)

-0.18s

Negative means A wins

Trap Gap (A−B)

1.7mph

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

Visualizations

Results overview

12Car A ET
12.2Car B ET
-0.2ET Gap
1.7Trap Gap

ET Gap (A−B) vs. Car A Power

ET Gap (A−B)

-0.2s
-33

Formula

Hale predictions for both cars on identical assumptions — the delta is the fair comparison.

Each car: ET = 5.825 × (W ÷ HP)⅓; gaps by subtraction

Variables

SymbolNameUnitDescription
A/BContenderswhp/lbPower and weight each

Explanation

Equal tires, equal air, equal drivers assumed — the gap isolates power-to-weight.

Step-by-Step Calculation

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

Step 1

Record the inputs.

Car A Power:400 whp
Car A Weight:3500 lb
Car B Power:350 whp
Car B Weight:3200 lb
Result: 4 inputs ready
Step 2

Apply the formula.

Each car: ET = 5.825 × (W ÷ HP)⅓; gaps by subtraction
Result: Primary result = -0.18 s
Step 3

Read every derived output.

Car A ET:12.00 s
Car B ET:12.18 s
ET Gap (A−B):-0.18 s
Trap Gap (A−B):1.7 mph
Result: ET Gap (A−B) = -0.18 s
Final Answer
12.00

Worked Examples

See how the calculator works with different scenarios.

Scenario

A: 400 whp/3,500 lb vs B: 350 whp/3,200 lb.

Inputs

A:400/3,500
B:350/3,200

Calculation

A: 12.00 @ 113.5 · B: 12.15 @ 111.6

Result

A wins by 0.15 s and 1.9 mph.

Interpretation

Power edges lightness here — but B launches easier.

Understanding Your Result

Your Result: Car A ET: 12.00 s

What This Means

Predicted head-to-head outcome on power-to-weight.

Why It Matters

Settles bench debates and sets realistic expectations before grudge night.

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

Bench racing deserves real numbers: two power-to-weight ratios, two timeslips, one verdict.

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.

What about drivers?
Excluded by design — this isolates the cars. Add ~0.3 s variance for mortals.
Tires equal?
Assumed. A tire advantage can swing a close matchup either way.

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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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