Free engineering calculators for UK mechanical, electrical and construction work - sizing, checking and costing tools that run entirely in your browser. Nothing to install, no sign-up, and nothing you enter is uploaded or stored.
- MechanicalHeat loss, pipework, pumps, vessels and support loads.40 calculators
- ElectricalCable sizing, voltage drop, fault current and demand.19 calculators
- DuctworkDuct sizing, pressure drop, leakage, heat and weight.14 calculators
- InsulationPipe and duct insulation, condensation and surface temperature.7 calculators
- SustainabilityOperational and embodied carbon, payback and BREEAM.11 calculators
- Contractor ToolsProgramme, resource, procurement and commercial.20 calculators
About these calculators
Every calculator here runs entirely in your browser. There is nothing to install, no sign-up, and nothing you type is uploaded or stored - close the tab and it is gone.
They are grouped by discipline so you can get to the right one quickly. Mechanical covers heat loss, pipework, pumps and vessels. Electrical covers cable sizing, volt drop, fault current and demand. Ductwork covers duct sizing, pressure drop, ventilation rates and leakage. Insulation covers thickness, condensation risk and surface temperature. Sustainability covers operational and embodied carbon, payback and assessment. Contractor Tools covers the commercial side - estimating, valuation, retention and programme.
Each one states the standard or method it works to on the page itself, so you can check the working rather than take a number on trust. They are built for engineers, estimators and contractors who need a defensible figure quickly - during a tender, on site, or as a sense-check on someone else's.
They are design aids. They will get you to a sound working figure and show you how it was reached, but the finished design remains the responsibility of a competent engineer.
Frequently asked questions
Are these calculators really free?
Yes. All of them, with no sign-up and no limit on use. They are built and maintained by Ensign Software as a resource for the trades we work with.
Is my data sent anywhere?
No. Every calculation runs in your browser. Nothing you enter is uploaded, transmitted or stored, and closing the tab discards it.
Can I rely on these for a design?
Treat them as design aids. Each states the standard or method it applies so the arithmetic can be checked, but anything issued for construction should be verified by the responsible engineer.
Which standards do they follow?
It depends on the tool - BS 7671 for electrical work, CIBSE guidance for mechanical and ductwork, BS 5422 for insulation, and RICS and JCT conventions for the commercial calculators. Each page names its own source.