A21 bulb shape
A21 is a pear-shaped household bulb that is visibly wider than A19 — 2.625 inches maximum diameter — typically used where higher output is needed.
Exact specs
| Shape code | A21 |
|---|---|
| Maximum diameter | 2.625 in (67 mm) |
| Length (approximate) | 5.0 in (127 mm) |
| Common base pairing | E26 (NA), E27 (EU) |
| Typical use | High-output lamps, open fixtures, floor lamps |
What fixtures commonly use it
Floor lamps, torchiere-style fixtures, and open ceiling lights commonly use A21 when higher lumen output is needed from a standard E26 socket.
What it's interchangeable with
A21 uses the same E26/E27 base as A19. In open fixtures, they are functionally interchangeable. In enclosed shades, A21 may be too wide.
What it's NOT interchangeable with
A21 should not be put in enclosed, glass-globe, or narrow shade fixtures designed for A19 — measure available diameter clearance first.
Common mistakes
- Purchasing A21 for a drum shade that only clears A19 width.
- Assuming any E26 fixture handles A21 — enclosed fixtures may overheat with minimal clearance.