Electrical reference tables

How to use these references

A reference table answers a question of fact: what a 12 AWG conductor is rated for, what a brown wire means in a UK consumer unit, whether 4.7 kΩ is a standard value, which pin of a USB-C plug carries power. Each page puts the table first, then explains how to read it, where every column comes from and which edition of which standard it follows. When the table feeds a calculation, the page links to the calculator that does it, and the calculator links back, so you can move from looking a value up to using it without retyping anything.

Two habits make these tables safer to use. First, check the edition. Wire ampacity and colour rules are set by codes that are revised every few years and adopted on different dates in different places, so a value is only right for the code your inspector enforces. Our pages name the edition next to every number, and the NEC adoption tracker shows which edition each US state uses. Second, treat a table as the starting point, not the last word: a manufacturer’s datasheet or the adopted code text always wins.

Wiring and installation

The wire size chart lists American Wire Gauge and kcmil conductors with their physical data and the NEC ampacity columns, cited by table and edition. It is the lookup behind sizing a circuit; the ampacity it shows is a starting point that correction and adjustment factors can reduce.

The wire colour codes page compares the colours used for line, neutral and protective conductors in the United States, Canada, the United Kingdom, Europe, Australia and New Zealand, and India, and covers DC and solar circuits. It separates the colours a code requires from the ones that are only common practice, because the difference matters when you open an unfamiliar panel. It also says plainly what every electrician learns early: colours identify intent, not condition, so test before you touch.

Electronics

Component values come from the IEC 60063 preferred-number series. The E-series value tables list every value from E3 to E192, explain which tolerance each series goes with, and show how to pick the nearest standard value. The codes printed on parts each have a calculator that works both ways: the resistor colour code calculator for banded resistors, the SMD resistor code calculator for chip markings including EIA-96, and the capacitor code calculator for picofarad codes, tolerance and voltage letters and ceramic dielectrics. Where makers disagree, for example on the power rating of a given chip size or the meaning of an EIA-96 letter, the pages show every reading rather than picking one.

Connectors and pinouts

The pinout diagrams cover connectors and boards you meet daily, from USB-C and RJ45 to the Raspberry Pi header and the OBD-II port. Tap any pin to see what it does, then read the full table underneath; each one is checked against the published specification, with variants noted where they differ.

Codes and standards

Many tables here depend on which installation code applies. The electrical codes by country page explains which code governs where (the NEC, the Canadian Electrical Code, BS 7671, IEC 60364 and AS/NZS 3000) and translates the vocabulary between them, so a “grounding conductor” in one table and a “protective conductor” in another are recognisably the same thing.

How we build and check reference data

Values come from primary documents wherever we can reach them: standards publishers’ previews and catalogues, NFPA’s published drafts and errata, and manufacturers’ datasheets. A value needs two independent sources before we present it as settled; anything resting on one source is marked as such on the page, and our calculators warn when such a value drives a result. We never reproduce the text or tables of copyrighted codes: requirements are summarised in our own words with the section number, so you can check them in the edition you work to. Read the methodology for the details, and if you spot an error, report it: every correction is logged publicly.