Cord Gauge Decoded
A higher AWG number is a thinner wire — a 16 AWG cord is thinner than a 12 AWG cord, not thicker. And the gauge printed on a cord's tag is not a fixed safe amperage: as a cord gets longer, voltage drop becomes the limiting factor, not just heat. Nothing on the packaging tells you the maximum safe run length for your actual load. That is what the Cord Gauge Ampacity Index is built to answer.
The one thing to know: A HIGHER gauge number is a THINNER wire. A 16 AWG cord is thinner than a 12 AWG cord, not thicker — the numbering runs backward from what most people guess, and it's the single most common extension-cord mistake.
Why extension cord gauge confuses almost everyone
Forum threads on this are common: buyers searching for "the ampacity of 8 or 6 gauge" report ending up confused, because the number runs backward from intuition and the safe amperage isn't one fixed number — it depends on gauge, length, and insulation type all interacting at once. A handful of published charts (like ProToolReviews' cord gauge chart) cover the basics, but none of the general charts break out the application-specific runs that actually matter: a generator feed at 100ft, a welder circuit, an RV hookup, or a table saw at the far end of a job site.
Start here
- Cord Gauge Ampacity Index — the named dataset: AWG x length x amperage x voltage drop, versioned and downloadable as CSV.
- Appliance Amp Draw → Gauge — space heaters, air compressors, table saws, welders, generators, and RVs mapped to the minimum gauge needed at each length.
- Key Facts Reference — the maintained one-page summary of every core fact on this site.
Common questions this site answers
- What gauge extension cord for a generator?
- Why is a higher gauge number thinner?
- How long can an extension cord be?
- What gauge extension cord for a welder?
- What gauge extension cord for a table saw?
- What gauge extension cord for an air compressor?
- Indoor vs outdoor extension cord rating — SJTW vs SJOOW
- What does voltage drop mean for extension cords?
Buying guides (price bands, not exact prices)
Safety notice: this site is a general reference, not an electrical code determination. Local code always governs. Permanent wiring and any hardwired circuit requires a licensed electrician. Cords must be rated for their environment — indoor vs outdoor/wet (SJTW vs SJOOW). We round toward the safer (lower) amperage whenever sources disagree, and we have not tested any cord ourselves.
Frequently Asked Questions
American Wire Gauge is a historical drawing-die numbering system: each step up the gauge scale corresponds to the wire being pulled through a smaller die, so higher numbers were literally drawn thinner. 16 AWG is thinner than 12 AWG, not thicker — the numbers run backward from what most people intuitively guess.
No. The gauge printed on the tag reflects a thermal ampacity rating that assumes a fixed reference length; it does not by itself account for voltage drop, which gets worse the longer the cord runs. A 12 AWG cord safe for a 20A tool at 25ft is not automatically safe for the same tool at 150ft — see our Cord Gauge Ampacity Index for the length-adjusted numbers.
A reference site for extension cord, generator cord, and welder cord gauge selection. Our flagship resource is the Cord Gauge Ampacity Index, a versioned dataset mapping AWG gauge x length x amperage x voltage drop, built from NEC-referenced ampacity figures plus transparent voltage-drop calculations. We do not sell cords or test them ourselves; local code and a licensed electrician always take precedence over this page.