A21 Bulb
A slightly larger version of the standard A19 bulb — 2.625 inches in diameter. Used for higher-wattage LED bulbs that need more space for heat dissipation.
The A21 is the A19's bigger sibling — same pear shape, same E26 base, but about a quarter-inch wider at 2.625 inches (67mm). Manufacturers use the A21 size when they need more room inside the bulb for higher-output LED chips and larger heat sinks.
You'll typically find A21 in 75W-equivalent and above LED bulbs. The extra volume helps with thermal management, which directly affects lifespan and light quality at higher outputs. If a 100W-equivalent LED seems unusually bulky, it's probably an A21.
The practical concern is fitment. Most fixtures designed for A19 can handle an A21 — the base is identical. But tight lamp harps, narrow recessed trims, and small enclosed globes might not accommodate the wider body. Always measure if you're buying high-output bulbs for an existing fixture.
Specifications
| Diameter | 2.625 in (67mm) |
| Common base | E26 |
| Typical use | 75W-150W equivalent LEDs |
Related Terms
- A19 Bulb
The standard household light bulb shape — a pear-shaped bulb 2.375 inches in diameter, used in most lamps and fixtures.
- E26 / E27 Base
The standard Edison screw base used in most household lamps and fixtures. E26 (26mm) is the North American version, E27 (27mm) is the European equivalent.
