Sources & Standards

Wire size standards

• IEC 60228 — Conductors of insulated cables. The international metric standard that defines the cross-sectional areas (mm²) used across UK installations and the BS 7671 framework. Wire Math uses the IEC 60228 ladder as the canonical metric reference.
• BS 3737 — Standard Wire Gauge. The legacy British SWG table reproduced in our SWG lookup. SWG is no longer the working standard for UK installations but persists in older drawings, reference books, and imported components.
• AWG (American Wire Gauge) — geometric definition: diameter in mm equals 0.127 · 92^((36 − awg)/39). Wire Math computes AWG from this definition rather than from a static lookup table so non-integer and out-of-range queries can be handled with a reported delta.

Electrical references

• BS 7671 — Requirements for Electrical Installations. Referenced as framing for UK voltage-drop and ampacity context. Wire Math does not reproduce its tables or perform compliance checks. See the disclaimer for what that means in practice.
• Conductor resistivity values for copper and aluminium follow the IEC standard reference values at 20 °C. Temperature coefficients (α_cu, α_al) are the commonly cited values used in UK design references.

Where derating sits

Cable derating for grouping, ambient temperature, installation method, and circuit protection is the domain of BS 7671 and the On-Site Guide. Wire Math intentionally stops short of derating to avoid presenting a calculator output as a compliance verdict. Use the appropriate standards documents and a competent person for design and verification.

Reporting source issues

If a constant or table row looks wrong, please tell us via /contact and include the build identity shown in the footer so we can pin the exact registry version your report relates to.