Unit converter
Engineering unit converter: length, area, volume, mass, force, pressure and stress, torque, temperature, speed, surface finish (Ra, RMS, microinch), hardness scales, thread pitch and TPI, and decimal to fraction.
Unit converter
Metric and standard, plus the shop conversions the generic apps miss: surface finish, hardness scales, thread pitch, taper and decimal to fraction.
Linear units are exact factors (1 in = 25.4 mm, 1 lbf = 4.44822 N, 1 psi = 6.89476 kPa).
Surface finish: Ra µin = Ra µm / 0.0254, RMS ≈ 1.11 · Ra for a typical machined surface. ISO N grades: N1 = 0.025 µm up to N12 = 50 µm, doubling each step.
Hardness conversions use ASTM E140 relations for non-austenitic steel, interpolated. They do not apply to aluminum, copper alloys or austenitic stainless. Tensile strength is an estimate only.
Thread: TPI = 25.4 / pitch (mm). Taper: included angle = 2 · atan( (in/ft) / 24 ) for taper on diameter, grade % = tan(angle) · 100.
Fractions are rounded to the nearest 1/64, 1/32, 1/16 or 1/8 with the error shown. Hardness values are approximate correlations, not measurements.
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