Stick with SJTW for extension cords.

It’s the one rating that covers indoor, outdoor, heavy use, and doesn’t break the bank.

“SJTW” is a code that tells you exactly what the cord can handle. S means “service cord” (600V rating for appliances), J means “junior” (300V, which is fine for home use – you don’t need the full 600V), T means “thermoplastic jacket” (lightweight, flexible), and W means “weather-resistant” (UV and moisture protected).

Other common ratings you’ll see:

• SJTW – Your daily driver. Outdoor safe, general purpose, affordable. Buy this.
• SJTOW – The O means oil-resistant. Overkill for home use unless you’re in a garage or workshop with fluids.
• SJTW-A – The A means “appliance cord.” Same as SJTW but often lighter gauge for small devices.
• STW – No J means full 600V rating. Thicker, heavier, for industrial or long runs.
• SJO – The O with no W means not weather-resistant. Fine indoors, but don’t leave it in the rain.
• SO – Heavy duty, oil and water resistant, but overpriced for home users.

For 99% of home, yard, and garage needs, SJTW is the sweet spot. You don’t need SO or STW unless you’re running a compressor 100 feet uphill in a monsoon.

Don’t overthink it. Look for the W and the J. The rest is noise.