Free Engine & Performance Calculators
Calculate engine displacement, HP from torque, compression ratio, 0-60 times, gear ratios, and turbo sizing. Built for car enthusiasts, mechanics, and engineers.
Quick Answer
Engine displacement = (π/4) × bore² × stroke × cylinders. Horsepower = (Torque × RPM) ÷ 5,252. A turbo adds 30-50% more power at 10 PSI boost.
Example: 86mm bore × 86mm stroke × 4 cylinders = 1,998 cc (2.0L engine). At 300 lb-ft × 4,000 RPM = 228 HP.
Try the Engine Displacement Calculator → or Calculate HP from Torque →
Common Engine Specs — Quick Lookup
| Engine | Displacement | HP | Torque | Compression |
|---|---|---|---|---|
| Honda K20 (Civic Si) | 2.0L I4 | 200 HP | 155 lb-ft | 11.0:1 |
| Ford EcoBoost 2.3T | 2.3L I4 Turbo | 310 HP | 350 lb-ft | 9.5:1 |
| GM LS3 (Corvette) | 6.2L V8 | 430 HP | 424 lb-ft | 10.7:1 |
| BMW B58 (M340i) | 3.0L I6 Turbo | 382 HP | 369 lb-ft | 11.0:1 |
| Toyota 2JZ-GTE (Supra) | 3.0L I6 Twin-Turbo | 320 HP | 315 lb-ft | 8.5:1 |
Stock factory specs. Use the HP Calculator to compute power from your own torque and RPM values.
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Popular Engine Calculations — Quick Reference
| Calculation | Formula | Example |
|---|---|---|
| Engine Displacement | (π/4) × bore² × stroke × cylinders | 86mm × 86mm × 4 = 1,998 cc |
| Horsepower from Torque | (Torque × RPM) ÷ 5,252 | 300 lb-ft @ 4,000 RPM = 228 HP |
| Compression Ratio | (swept + clearance) ÷ clearance | 500cc + 50cc = 11:1 CR |
| HP to kW | HP × 0.7457 | 300 HP = 223.7 kW |
| Injector Size | (HP × BSFC) ÷ (injectors × duty cycle) | 400 HP NA V8 ≈ 310 cc/min |
| Turbo Power Gain | ~40-50% increase at 10 PSI boost | 200 HP NA → ~280-300 HP turbo |
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About EngineCalc
EngineCalc provides free, accurate engine and performance calculators for automotive enthusiasts, mechanics, and engineers. Whether you are building a race engine, tuning a street car, or simply curious about engine mathematics, all results are instant with no sign-up required.
Engine Displacement and Compression Ratio
Engine displacement is the total volume swept by all pistons in one complete cycle, calculated as: displacement = (π ÷ 4) × bore² × stroke × number of cylinders. A typical modern 2.0-litre four-cylinder engine has a bore of around 86 mm and a stroke of 86 mm — a "square" engine where bore equals stroke. Compression ratio (CR) is the ratio of the cylinder volume at Bottom Dead Centre (BDC) to the volume at Top Dead Centre (TDC): CR = (swept volume + clearance volume) ÷ clearance volume. Higher compression ratios improve thermodynamic efficiency — each unit of fuel releases more energy — but increase the risk of detonation (knock) in petrol engines. Modern direct-injection engines achieve CRs of 12:1–14:1 by precisely controlling fuel timing to resist knock.
Horsepower, Torque, and the RPM Relationship
Torque and horsepower are related by RPM through the formula: HP = (Torque × RPM) ÷ 5,252 (in US customary units). This means a car producing 300 lb-ft of torque at 4,000 RPM makes: (300 × 4000) ÷ 5252 = 228 HP at that RPM. Torque curves peak earlier in the RPM range than power curves — diesel engines are typically high-torque, low-RPM; performance petrol engines sacrifice torque for high-RPM power. For real-world acceleration, torque at the wheels (after transmission and final drive ratios) is what matters, not engine torque alone.
Turbocharging, Boost, and Injector Sizing
A turbocharger forces more air into the engine, allowing more fuel to be burned and producing more power from the same displacement. Boost pressure is measured in PSI or bar above atmospheric pressure (14.7 PSI at sea level). Each additional atmosphere of boost roughly doubles the potential power output (less in practice due to intercooling losses and efficiency). Fuel injectors must be sized to supply sufficient fuel at maximum power demand: injector size (cc/min) = (HP × BSFC) ÷ (number of injectors × duty cycle), where BSFC (brake-specific fuel consumption) is typically 0.45–0.55 lb/HP/hr for naturally aspirated engines and 0.55–0.65 for turbocharged engines.
Frequently Asked Questions
How do I calculate engine displacement?
Engine displacement is calculated using the formula: Displacement = (pi / 4) x Bore² x Stroke x Number of Cylinders. Enter bore diameter, stroke length, and cylinder count into the Engine Displacement Calculator for an instant result in cc or liters.
What is a good compression ratio for a street car?
Most modern gasoline street cars run compression ratios between 10:1 and 13:1. Higher ratios improve fuel efficiency but require premium fuel. Turbocharged engines typically use lower ratios (8:1 to 10:1) to avoid knock under boost.
How do I convert horsepower to kilowatts?
Multiply mechanical horsepower by 0.7457 to get kilowatts. For example, 300 HP = 300 x 0.7457 = 223.7 kW. Use the HP to kW Converter for instant bidirectional conversion including metric horsepower (PS).
What size fuel injectors do I need for my engine?
Injector size depends on target horsepower, number of injectors, BSFC, and duty cycle. The formula is: Injector Size (cc/min) = (HP x BSFC) / (Number of Injectors x Duty Cycle). A 400 HP naturally aspirated V8 with 8 injectors at 80% duty cycle typically needs around 310 cc/min injectors.
How much horsepower does a turbo add?
A turbocharger can increase engine power by 30-50% or more depending on boost pressure, intercooling, and fueling. At 10 PSI of boost on a properly tuned engine, you can expect roughly a 40-50% power increase over the naturally aspirated baseline.