Litres consumed per 100 kilometres; lower is better. Standard metric efficiency unit.

Energy lost deforming tires as they roll. Low-pressure or wide tires raise it.

Automotive Calculators

Race Car Power-to-Weight Calculator

2026-09-27 6 min

Pounds per horsepower and horsepower per ton from race weight and power.

Weight Per HP: 6.22 lb/hp
Power Per Ton: 321.4 hp/ton

Calculator

Horsepower(hp)

Race Weight(lb) Help

With driver and fuel

Results update live as you type

Live statistics

Weight Per HP

6.22 lb/hp

Power Per Ton

321.4 hp/ton

Results

Optimal

Weight Per HP

6.22lb/hp

Power Per Ton

321.4hp/ton

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

Visualizations

Results overview

6.2Weight Per HP

321.4Power Per Ton

Weight Per HP vs. Horsepower

Weight Per HP

6.2lb/hp

020

Formula

Two standard normalizations of the same power-to-weight ratio.

lb/hp = weight / hp; hp/ton = hp / (weight / 2000)

Variables

Symbol	Name	Unit	Description
R	Pounds per hp	lb/hp	Lower is faster
P	HP per ton	hp/ton	Classing and comparison metric

Explanation

2,800 lb and 450 hp is 6.22 lb/hp or 321 hp/ton — solid club-racing territory.

Step-by-Step Calculation

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

Step 1

Record the inputs.

Horsepower:450 hp

Race Weight:2800 lb

Result: 2 inputs ready

Step 2

Apply the formula.

lb/hp = weight / hp; hp/ton = hp / (weight / 2000)

Result: Primary result = 6.22 lb/hp

Step 3

Read every derived output.

Weight Per HP:6.22 lb/hp

Power Per Ton:321.4 hp/ton

Result: Weight Per HP = 6.22 lb/hp

Final Answer

6.22

Worked Examples

See how the calculator works with different scenarios.

Scenario

2,800 lb with driver, 450 hp.

Inputs

Power:450 hp

Weight:2,800 lb

Calculation

2,800 / 450 = 6.22 lb/hp; 450 / 1.4 = 321 hp/ton

Result

6.22 lb/hp.

Interpretation

Every 60 lb shed is worth roughly 10 hp here.

Understanding Your Result

Your Result: Weight Per HP: 6.22 lb/hp

What This Means

How much mass each horsepower must accelerate.

Why It Matters

The single best predictor of straight-line pace and class competitiveness.

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

Power-to-weight distills the car to one competitiveness number.

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)

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

Practical Tips

•Weigh with driver and session-start fuel
•Compare in one metric only — do not mix lb/hp with hp/ton
•Weight loss helps braking and corners too, power does not

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.

Is lighter or more powerful better?

Equal ratio, lighter is better — weight helps every corner while power only helps straights.

What is a good club-racing ratio?

Roughly 6-9 lb/hp for fast HPDE/club cars; under 5 is serious race-car territory.

Related Calculators

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Related Guides

Deepen your understanding with these educational resources.

Automotive Guides

Build planning, measurement protocol and validation how-tos

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.

EPA — FuelEconomy.gov DOE — Fuel-Efficient Driving Tips NHTSA — Driving Safety & Efficiency SAE International — Fuel Economy Standards Consumer Reports — MPG Truth IRS — Standard Mileage Rates

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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Page Information

Last Updated:

2026-09-27

Version:

2.0.0

References:

License:

Free to use for educational and professional purposes.