Brake Horsepower Calculator
Calculate brake horsepower from torque and RPM readings. Supports lb-ft and Nm, with kW conversion, wheel HP, and power-to-weight ratio.
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Applications
Used by automotive enthusiasts, mechanics, and engineers to estimate engine power from dynamometer readings. Calculate BHP from torque and RPM, convert to kW, estimate wheel horsepower with drivetrain losses, and compute power-to-weight ratios for vehicle performance comparisons.
The Formula
BHP = (Torque × RPM) ÷ Constant. For US customary units (lb-ft): Constant = 5252 (derived from 1 hp = 550 ft·lb/s, where 5252 = 33,000 ÷ 2π). For metric units (Nm): Constant = 7127 (derived from the kW-to-hp conversion factor). kW = BHP × 0.7457. WHP = BHP × (1 - Drivetrain Loss / 100). Power-to-Weight = (BHP / Weight in lb) × 1000.
Fun Fact: At exactly 5,252 RPM, the torque value in lb-ft numerically equals the horsepower — this is why the famous 5252 constant appears in the formula! This relationship holds because horsepower is defined as torque times RPM divided by 5252.
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