⚙ Engineering
Quick checks for structural, mechanical, fluid, HVAC and electrical work: beam deflection, moments of inertia, pipe pressure drop, pump power, voltage drop, three-phase power and more. Each tool states its assumptions and cites its source, such as OpenStax University Physics, the U.S. Department of Energy, NASA or the USDA Forest Products Laboratory. Use them for estimates and learning; final designs need a licensed engineer and the applicable codes.
26 free engineering calculators
Battery Runtime CalculatorHow long a battery lasts from its amp-hour rating and load in amps or watts, with usable depth of discharge, inverter efficiency and Peukert correction.Beam Deflection CalculatorMaximum deflection, bending moment and reactions of a simply supported beam under a uniform or center point load, with an L/360 check.Bending Stress CalculatorMaximum bending stress σ = M·c/I = M/S in a beam for a rectangle, round bar, tube or any section, with section modulus and utilization.Bolt Torque CalculatorTightening torque for a target bolt preload with the short-form formula T = K·D·F, using nut factors from NASA’s Fastener Design Manual.CFM and Air Changes per Hour CalculatorConvert between airflow (CFM, m³/h or L/s) and air changes per hour (ACH) for a room, plus time to clear 99% of airborne contaminants.Column Buckling Calculator (Euler)Euler critical buckling load of a slender column for pinned, fixed or free ends, with slenderness ratio and critical stress.Gear Ratio CalculatorGear ratio from tooth counts for one or two stages, with output speed and output torque including efficiency.Heat Loss Calculator (U-value / R-value)Conductive heat loss through a wall, roof or window from area, temperature difference and U-value or R-value (US or SI).Hydrostatic Pressure CalculatorPressure at depth in a liquid with P = ρgh: gauge and absolute pressure for water, seawater or any fluid density.LED Resistor CalculatorCurrent-limiting resistor for one LED or a series string: exact ohms, nearest standard E12/E24 value, actual current and resistor wattage.Manning’s Equation Calculator (Open Channel Flow)Open-channel velocity and discharge with Manning’s equation for rectangular, trapezoidal, triangular and part-full circular sections.Moment of Inertia CalculatorSecond moment of area, section modulus and radius of gyration for rectangles, solid round bars, pipes/tubes and I-beams.Pipe Flow Rate CalculatorFlow rate from pipe diameter and velocity (Q = A·v), or the inside diameter needed to carry a flow at a target velocity.Pipe Pressure Drop CalculatorFriction pressure drop and head loss in a straight pipe using Darcy–Weisbach with the Swamee–Jain friction factor and a pipe roughness table.Power Factor Correction CalculatorCapacitor kVAR and microfarads needed to raise a load’s power factor to a target, with line current and kVA before and after correction.Pump Power CalculatorHydraulic (water) power, pump shaft (brake) power and motor input power from flow rate, total head, specific gravity and efficiency.RC and RL Time Constant CalculatorTime constant τ = RC or L/R, 5τ settling time, cutoff frequency and the percentage charged or discharged after any elapsed time.Reynolds Number CalculatorReynolds number for pipe flow from velocity, diameter, density and viscosity, with laminar, transitional or turbulent regime.Room AC BTU CalculatorRoom air conditioner size in BTU/h from floor area using the ENERGY STAR sizing chart, adjusted for sun, shade, occupants and kitchens.Shaft Torsion CalculatorMaximum shear stress (τ = T·r/J) and angle of twist (θ = TL/GJ) in a solid or hollow circular shaft under torque.Stress and Strain CalculatorCalculate axial stress, strain and Young’s modulus from force, cross-sectional area, original length and change in length.Thermal Expansion CalculatorChange in length (ΔL = αLΔT) of steel, aluminum, copper, concrete, glass and more for a temperature change, plus area and volume expansion.Three-Phase Power CalculatorReal power (kW), apparent power (kVA) and reactive power (kVAR) of a balanced three-phase load from line voltage, current and power factor.Torque, Power and RPM CalculatorConvert between shaft torque, speed and power with P = τ·ω, in N·m or lbf·ft, rpm or rad/s, kW or horsepower.Transformer Full-Load Current CalculatorPrimary and secondary full-load amps for a single-phase or three-phase transformer from its kVA rating and voltages, plus the turns ratio.Voltage Drop CalculatorVoltage drop and percent drop for copper or aluminum conductors by AWG/kcmil size, length and current, single-phase or three-phase.