AmpSizer

2023 NEC · free reference

The tables, in full.

Every figure AmpSizer calculates from, published openly with its source table cited. No paywall on any of it - a safety-relevant lookup belongs in the open. If you are not sure which of the three temperature columns your job is allowed to use, start with which ampacity column applies.

28
Conductor sizes, 14 AWG to 2000 kcmil
165
Ampacity values across both materials
8
Reference tables
432
Generated reference pages

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All tables

NEC 2023Every table listed here is transcribed from the 2023 NEC (NFPA 70, 2023). The code is republished on a three-year cycle and adoption varies by jurisdiction - confirm against your locally adopted edition and your authority having jurisdiction (AHJ) before you build.

Copper ampacityAllowable ampacity of copper conductors from 14 AWG to 2000 kcmil at 60°C, 75°C, and 90°C insulation ratings.Aluminum ampacityAllowable ampacity of aluminum and copper-clad aluminum conductors from 12 AWG to 2000 kcmil at 60°C, 75°C, and 90°C.Temperature correctionCorrection factors applied to conductor ampacity when the ambient temperature is above or below the 30°C table basis.Bundling adjustmentAdjustment factors applied when more than three current-carrying conductors share a raceway or cable.Breaker sizesThe standard ampere ratings for fuses and inverse-time circuit breakers, from 15 A to 6000 A.Grounding conductorsMinimum equipment grounding conductor size in copper and aluminum, by the rating of the overcurrent device ahead of the equipment.Conduit fillPermitted fill percentages, conduit internal areas for EMT, PVC Schedule 40, and RMC, and conductor cross-sectional areas by insulation type.Conductor propertiesCircular-mil area and DC resistance per 1000 feet for copper and aluminum conductors, the inputs to every voltage-drop estimate.

Per-conductor pages

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14 AWG copper12 AWG copper10 AWG copper8 AWG copper6 AWG copper4 AWG copper3 AWG copper2 AWG copper1 AWG copper1/0 AWG copper2/0 AWG copper3/0 AWG copper4/0 AWG copper250 kcmil copper300 kcmil copper350 kcmil copper400 kcmil copper500 kcmil copper600 kcmil copper700 kcmil copper750 kcmil copper800 kcmil copper900 kcmil copper1000 kcmil copper1250 kcmil copper1500 kcmil copper1750 kcmil copper2000 kcmil copper
12 AWG aluminum10 AWG aluminum8 AWG aluminum6 AWG aluminum4 AWG aluminum3 AWG aluminum2 AWG aluminum1 AWG aluminum1/0 AWG aluminum2/0 AWG aluminum3/0 AWG aluminum4/0 AWG aluminum250 kcmil aluminum300 kcmil aluminum350 kcmil aluminum400 kcmil aluminum500 kcmil aluminum600 kcmil aluminum700 kcmil aluminum750 kcmil aluminum800 kcmil aluminum900 kcmil aluminum1000 kcmil aluminum1250 kcmil aluminum1500 kcmil aluminum1750 kcmil aluminum2000 kcmil aluminum

About this data

These are published numeric values transcribed from the 2023 NEC - table data, not code text. AmpSizer reproduces no code language, and it is not affiliated with, endorsed by, or a substitute for the code itself. If you need the actual requirements, including the exceptions and conditions the tables reference, you need the code document.

The whole dataset lives in one generated file with the edition labelled, so moving to a new edition is a single update rather than a hunt through the app. Every value is checked against known anchor figures and for internal consistency - ampacity has to rise with conductor size, copper has to beat aluminum at the same size, and columns have to order correctly. Those checks are assertions in this site's test suite, in src/lib/nec.test.ts, which anyone can run with npm test; a value that drifts fails there, and a change that breaks one does not get merged.

Adoption is not uniform. Jurisdictions adopt editions years apart and amend them freely, so the edition cited here may not be the one enforced where you are. Confirm before you rely on any figure.