Engine Horsepower Calculator — Torque × RPM, Wheel vs. Crank HP

Calculate engine horsepower from torque and RPM. Switch units (lb·ft / N·m), estimate drivetrain (wheel vs. crank) losses, and convert between hp and kW. Includes formulas, examples, glossary, and FAQs.

Full original guide (expanded)

Audit: Complete
Formula (LaTeX) + variables + units
This section shows the formulas used by the calculator engine, plus variable definitions and units.
Formula (extracted LaTeX)
\[P_{\mathrm{hp}}=\frac{T_{\mathrm{lb\cdot ft}}\cdot n_{\mathrm{rpm}}}{5252}\]
P_{\mathrm{hp}}=\frac{T_{\mathrm{lb\cdot ft}}\cdot n_{\mathrm{rpm}}}{5252}
Formula (extracted LaTeX)
\[P_{\mathrm{kW}}=\frac{T_{\mathrm{N\cdot m}}\cdot n_{\mathrm{rpm}}}{9549}\]
P_{\mathrm{kW}}=\frac{T_{\mathrm{N\cdot m}}\cdot n_{\mathrm{rpm}}}{9549}
Formula (extracted text)
Imperial horsepower (hp) from torque in lb·ft and rotational speed in rpm: \[ P_{\mathrm{hp}}=\frac{T_{\mathrm{lb\cdot ft}}\cdot n_{\mathrm{rpm}}}{5252} \] where \(5252=\frac{33{,}000~\mathrm{ft\cdot lbf/min}}{2\pi~\mathrm{rad/rev}}\). SI kilowatts from torque in N·m and rpm: \[ P_{\mathrm{kW}}=\frac{T_{\mathrm{N\cdot m}}\cdot n_{\mathrm{rpm}}}{9549} \] (constant derives from unit conversion \(P=T\omega\) with \(\omega=2\pi n/60\)). Conversions: \(\;1~\mathrm{kW}=1.3410229~\mathrm{hp}\;\) and \(\;1~\mathrm{hp}=0.7456999~\mathrm{kW}\). Drivetrain correction (estimate): if wheel power \(P_w\) and loss fraction \(L\), then crank/bhp \(P_c=\frac{P_w}{1-L}\); conversely \(P_w=P_c(1-L)\).
Variables and units
  • No variables provided in audit spec.
Sources (authoritative):
Changelog
Version: 0.1.0-draft
Last code update: 2026-01-19
0.1.0-draft · 2026-01-19
  • Initial audit spec draft generated from HTML extraction (review required).
  • Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
  • Confirm sources are authoritative and relevant to the calculator methodology.
Verified by Ugo Candido on 2026-01-19
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Audit: Complete
Formula (LaTeX) + variables + units
This section shows the formulas used by the calculator engine, plus variable definitions and units.
Formula (extracted LaTeX)
\[P_{\mathrm{hp}}=\frac{T_{\mathrm{lb\cdot ft}}\cdot n_{\mathrm{rpm}}}{5252}\]
P_{\mathrm{hp}}=\frac{T_{\mathrm{lb\cdot ft}}\cdot n_{\mathrm{rpm}}}{5252}
Formula (extracted LaTeX)
\[P_{\mathrm{kW}}=\frac{T_{\mathrm{N\cdot m}}\cdot n_{\mathrm{rpm}}}{9549}\]
P_{\mathrm{kW}}=\frac{T_{\mathrm{N\cdot m}}\cdot n_{\mathrm{rpm}}}{9549}
Formula (extracted text)
Imperial horsepower (hp) from torque in lb·ft and rotational speed in rpm: \[ P_{\mathrm{hp}}=\frac{T_{\mathrm{lb\cdot ft}}\cdot n_{\mathrm{rpm}}}{5252} \] where \(5252=\frac{33{,}000~\mathrm{ft\cdot lbf/min}}{2\pi~\mathrm{rad/rev}}\). SI kilowatts from torque in N·m and rpm: \[ P_{\mathrm{kW}}=\frac{T_{\mathrm{N\cdot m}}\cdot n_{\mathrm{rpm}}}{9549} \] (constant derives from unit conversion \(P=T\omega\) with \(\omega=2\pi n/60\)). Conversions: \(\;1~\mathrm{kW}=1.3410229~\mathrm{hp}\;\) and \(\;1~\mathrm{hp}=0.7456999~\mathrm{kW}\). Drivetrain correction (estimate): if wheel power \(P_w\) and loss fraction \(L\), then crank/bhp \(P_c=\frac{P_w}{1-L}\); conversely \(P_w=P_c(1-L)\).
Variables and units
  • No variables provided in audit spec.
Sources (authoritative):
Changelog
Version: 0.1.0-draft
Last code update: 2026-01-19
0.1.0-draft · 2026-01-19
  • Initial audit spec draft generated from HTML extraction (review required).
  • Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
  • Confirm sources are authoritative and relevant to the calculator methodology.
Verified by Ugo Candido on 2026-01-19
Profile · LinkedIn
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Audit: Complete
Formula (LaTeX) + variables + units
This section shows the formulas used by the calculator engine, plus variable definitions and units.
Formula (extracted LaTeX)
\[P_{\mathrm{hp}}=\frac{T_{\mathrm{lb\cdot ft}}\cdot n_{\mathrm{rpm}}}{5252}\]
P_{\mathrm{hp}}=\frac{T_{\mathrm{lb\cdot ft}}\cdot n_{\mathrm{rpm}}}{5252}
Formula (extracted LaTeX)
\[P_{\mathrm{kW}}=\frac{T_{\mathrm{N\cdot m}}\cdot n_{\mathrm{rpm}}}{9549}\]
P_{\mathrm{kW}}=\frac{T_{\mathrm{N\cdot m}}\cdot n_{\mathrm{rpm}}}{9549}
Formula (extracted text)
Imperial horsepower (hp) from torque in lb·ft and rotational speed in rpm: \[ P_{\mathrm{hp}}=\frac{T_{\mathrm{lb\cdot ft}}\cdot n_{\mathrm{rpm}}}{5252} \] where \(5252=\frac{33{,}000~\mathrm{ft\cdot lbf/min}}{2\pi~\mathrm{rad/rev}}\). SI kilowatts from torque in N·m and rpm: \[ P_{\mathrm{kW}}=\frac{T_{\mathrm{N\cdot m}}\cdot n_{\mathrm{rpm}}}{9549} \] (constant derives from unit conversion \(P=T\omega\) with \(\omega=2\pi n/60\)). Conversions: \(\;1~\mathrm{kW}=1.3410229~\mathrm{hp}\;\) and \(\;1~\mathrm{hp}=0.7456999~\mathrm{kW}\). Drivetrain correction (estimate): if wheel power \(P_w\) and loss fraction \(L\), then crank/bhp \(P_c=\frac{P_w}{1-L}\); conversely \(P_w=P_c(1-L)\).
Variables and units
  • No variables provided in audit spec.
Sources (authoritative):
Changelog
Version: 0.1.0-draft
Last code update: 2026-01-19
0.1.0-draft · 2026-01-19
  • Initial audit spec draft generated from HTML extraction (review required).
  • Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
  • Confirm sources are authoritative and relevant to the calculator methodology.
Verified by Ugo Candido on 2026-01-19
Profile · LinkedIn
Formulas

(Formulas preserved from original page content, if present.)

Version 0.1.0-draft
Citations

Add authoritative sources relevant to this calculator (standards bodies, manuals, official docs).

Changelog
  • 0.1.0-draft — 2026-01-19: Initial draft (review required).