Math & Numbers
Convert horsepower to watts with configurable decimal precision
hp-to-wattMath & Numbers
Convert hours to days with configurable decimal precision
hours-to-daysMath & Numbers
Convert hectares to square meters with configurable decimal precision
hectare-to-square-meterMath & Numbers
Convert hectares to acres with configurable decimal precision
hectare-to-acreMath & Numbers
Calculate the harmonic mean of positive values, with optional arithmetic and geometric mean comparison
harmonic-mean-calculatorDate & Time
Calculate holidays for a specific year and country
holiday-calculatorMath & Numbers
Convert US liquid gallons to liters with configurable decimal precision
gallon-to-literMath & Numbers
Convert force between newton (N, SI base), kilonewton (kN), dyne (dyn, CGS = 10⁻⁵ N), pound-force (lbf = 4.4482216152605 N), kilogram-force (kgf = 9.80665 N), and poundal (pdl = 0.138254954376 N). All factors derive from the exact defining constants 1 lb = 0.45359237 kg, 1 ft = 0.3048 m, and standard gravity g₀ = 9.80665 m/s². Converts via newton to the target unit and lists the equivalent value in all six units. Reference: 1 kg of mass on Earth ≈ 9.80665 N (1 kgf); an adult weighs ≈ 700 N.
force-unit-converter-extendedMath & Numbers
Convert fuel consumption / fuel economy between L/100km, miles per US gallon (mpg US), miles per Imperial gallon (mpg UK), and km/L. mpg and L/100km are reciprocal (higher mpg = lower L/100km), so conversion goes through the km/L axis, not a single multiplier. Defining constants are exact by law: 1 US gallon = 3.785411784 L (NIST HB 44), 1 Imperial gallon = 4.54609 L (UK W&M Act 1985), 1 mile = 1.609344 km (1959 agreement). Reference: a compact car at ~6 L/100km ≈ 39 mpg US ≈ 47 mpg UK.
fuel-consumption-converterMath & Numbers
Estimate multi-segment trip fuel, cost, CO2, route-condition weighting, and carpool sharing.
fuel-cost-trip-calculatorMath & Numbers
Calculate the gear module m. m = d/z = p/π. Solve the module from the pitch diameter d and tooth count z, or from the circular pitch p. Also returns the pitch diameter, circular pitch and addendum.
gear-module-calculatorMath & Numbers
Calculate the gear ratio and output speed of a meshing gear pair. i = z₂/z₁ = n₁/n₂. Enter the tooth counts to get the ratio; add the driver speed to get the driven speed.
gear-ratio-calculator