Engineering Calculators
Free, verified engineering calculators with step-by-step guides and reference data.
Resistance Calculator — Ohm's Law, Series & Parallel
Solve Ohm's Law for V, I, or R, plus total series and parallel resistance for any number of resistors. Free instant calculator.
Quarter Mile Calculator: ET & Trap Speed Estimator
Estimate quarter-mile elapsed time and trap speed from weight and horsepower, or solve for the horsepower needed to hit a target ET.
Square Yard Calculator — Area Converter & Room Size
Convert square yards, feet, meters, and inches, or calculate area from length and width — plus carpet, turf, and flooring cost per square yard.
Unit Conversion Calculator — Amps, Torque, Pressure, Power
Convert amps to watts, ft-lb to joules/N·m, MPa/bar to PSI, kW to HP, and PSI to kPa — bidirectional, with exact NIST conversion factors.
Towing Capacity Calculator — Max Trailer Weight & Payload
Calculate your max trailer weight, payload capacity, and recommended tongue weight from your vehicle's GCWR, GVWR, and curb weight.
Voltage Drop Calculator — NEC Formula, Single & 3-Phase
Calculate voltage drop and percentage for any wire run using the NEC formula. Single-phase and three-phase, copper or aluminum, full AWG table.
Acreage Calculator — Land Area Converter & Parcel Size
Convert acres, square feet, hectares, and square yards, or calculate acreage from a rectangular parcel's length and width — plus a football-field comparison.
Power-to-Weight Ratio Calculator: hp/ton & W/kg
Calculate power-to-weight ratio for cars (hp/ton), cycling (W/kg with pro benchmark tiers), or general machinery (kW/kg). Instant results.
Chain Rule Calculator — Step-by-Step Derivatives
Calculate derivatives of composite functions using the chain rule. Picks outer and inner function, shows u-substitution steps, dy/du, du/dx, and final answer.
Density Altitude Calculator for Pilots
Calculate density altitude from elevation, altimeter setting, and OAT. Shows pressure altitude, ISA deviation, performance level, and humidity note.
Crosswind Component Calculator for Pilots
Calculate crosswind and headwind from wind direction, speed, and runway. Includes gust components, opposite runway, aircraft limit check, and clock method tip.
Pulley RPM Calculator: Speed Ratio, Belt Length & Torque
Calculate driven pulley RPM, belt length, speed ratio, and torque for any belt drive. Imperial and metric. Supports V-belt, flat belt, and timing belt drives.