T8 tube reference
T8 is a 1-inch diameter tubular fluorescent or LED tube, most commonly 4 feet (48 inches) long, used in commercial and office fixtures.
Exact specs
| Shape code | T8 (Tubular, 8⁄8-inch diameter) |
|---|---|
| Tube diameter | 1.0 in (25.4 mm) |
| Common lengths | 2 ft (24 in), 4 ft (48 in) |
| Base type | G13 bi-pin (fluorescent); single-end or double-end LED types vary |
| Voltage | Fluorescent: requires ballast. LED: ballast-bypass or ballast-compatible |
What fixtures commonly use it
Office ceiling fixtures, garage shop lights, warehouse lighting, and commercial task lighting use T8 tubes as the standard fluorescent format.
What it's interchangeable with
Type A T8 LED tubes use the existing fluorescent ballast. Type B T8 LED tubes require ballast bypass. Type A+B works both ways. Choose based on your fixture and desired maintenance approach.
What it's NOT interchangeable with
T8 is not interchangeable with T5 (smaller diameter, different base) or T12 (larger 1.5-inch diameter). The G13 pin spacing is the same as T12 but tube diameters differ.
Common mistakes
- Mixing T8 and T12 based on pin fit — T12 is wider and not a safe T8 substitute.
- Buying ballast-bypass LED without rewiring the fixture.
- Using a ballast-compatible LED in a fixture with a failed ballast.