AtlasCalcsUtility Calculation Suite
Automotive Calculators

Supercharger Boost Calculator

2026-09-27 6 min

Blower RPM and estimated boost from pulley diameters, engine RPM and blower rating.

Blower Speed
12000 RPM
Estimated Boost
11.2 psi

Calculator

Engine RPM(RPM)
RPM
Crank Pulley(in)
in
Blower Pulley(in)
in
Blower Max Boost(psi) Help
psi

Rated boost at max blower RPM

Results update live as you type

Live statistics

Blower Speed

12000 RPM

Estimated Boost

11.2 psi

Results

Optimal

Blower Speed

12000RPM

Estimated Boost

11.2psi

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

Visualizations

Results overview

12,000Blower Speed
11.2Estimated Boost

Estimated Boost vs. Engine RPM

Estimated Boost

11.2psi
025

Formula

Pulley ratio sets blower speed; positive-displacement boost scales near-linearly with speed against a fixed engine.

Blower RPM = engine × crank ÷ blower; boost ≈ blower-RPM share of rated

Variables

SymbolNameUnitDescription
crank/scPulley ratioratioDrive multiplication
ratedBlower ratingpsi@rpm15,000 RPM reference

Explanation

Smaller blower pulley = faster spin = more boost — until redline, belt slip or rotor coating limits.

Step-by-Step Calculation

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

Step 1

Record the inputs.

Engine RPM:6000 RPM
Crank Pulley:7 in
Blower Pulley:3.5 in
Blower Max Boost:14 psi
Result: 4 inputs ready
Step 2

Apply the formula.

Blower RPM = engine × crank ÷ blower; boost ≈ blower-RPM share of rated
Result: Primary result = 11.2 psi
Step 3

Read every derived output.

Blower Speed:12000 RPM
Estimated Boost:11.2 psi
Result: Estimated Boost = 11.2 psi
Final Answer
12000

Worked Examples

See how the calculator works with different scenarios.

Scenario

6,000 engine, 7 in crank, 3.5 in blower, 14 psi rated.

Inputs

Eng:6,000
Crank:7 in
Blower:3.5 in
Rated:14 psi

Calculation

blower = 12,000 RPM; boost = 0.80 × 14 = 11.2

Result

12,000 blower RPM · 11.2 psi.

Interpretation

Aggressive street setup — watch belt wrap and temps.

Understanding Your Result

Your Result: Blower Speed: 12000 RPM

What This Means

Blower speed and resulting boost for your pulley combo.

Why It Matters

Pulley swaps are the blower equivalent of turbo boost controllers — cheap and decisive.

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

Pulleys are gears made of rubber and aluminum — ratio sets blower speed, speed sets boost.

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.

Smaller pulley = more boost?
Yes — the blower pulley is the denominator. Smaller spins faster.
Belt slip?
Above ~10 psi, 6-rib belts slip — 8/10-rib conversions and idler wrap fix it.

Related Calculators

Explore more calculators related to this topic.

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

Was This Calculator Helpful?

Page Information