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The calculations people actually rerun

These are the everyday relationships: stress, deflection, flow, power, weight, stairs. Each page keeps the formula visible. None of them is a code check.

Calculation	On this site	It will not do
Ohm's law and resistors	Ohm, series and parallel	Cable sizing
Voltage drop	Copper estimate	BS 7671
Three-phase power and power factor	Power, kVAr	Harmonic study
Concrete volume	Volume	Mix design
Beam moment and deflection	Reactions, Deflection	Section check
Direct stress and modulus	Stress, E	Buckling
Rectangle I and Z	Section	Steel tables
Slope and stairs	Slope, Stairs	Approved Document approval
Pipe velocity, Reynolds, head	Flow, Reynolds, Head	Network design
Pump and shaft power	Pump, Shaft	Machine selection
Steel and rebar weight	Plate, Rebar	A bar schedule
Thermal expansion and sensible heat	Expansion, Heat	Restrained stress, phase change
Earthworks and runoff	Volume, Runoff	Mass haul, FEH
Percentage error	Error	An uncertainty budget
Circle section, resultant, mass	Circle, Resultant, Mass	Hollow sections, moisture
Heat loss, divider, single-phase power	Heat loss, Divider, Single phase	Compliance calc, loaded divider, cable size
Torque, gears, curve, Euler	Torque, Gears, Curve, Euler	Eurocode buckling, transition curves

Last checked 2 October 2026. Official design methods stay in the named standard. See standards these tools do not replace.