An A21 is the standard household bulb shape in a bigger size: 2-5/8" across against the A19’s 2-3/8", and longer. The A19s and A21s compared here come on the standard E26 base, so what to check is whether an A21 fits under the shade or inside the fixture.
The sizes in the code
The number is the bulb’s width at its widest point in eighths of an inch. Each step of 2 in the number adds a quarter inch, and the length isn’t in the code at all.
| Code | Across | Westinghouse LED | Length |
|---|---|---|---|
| A15 | 15/8 = 1-7/8" | 5.5OMNIA15, 600 lm | 3.55" |
| A19 | 19/8 = 2-3/8" | 9OMNIA19, 800 lm | 4.44" |
| A21 | 21/8 = 2-5/8" | 25OMNIA21, 2,550 lm | 5.47" |
| A23 | 23/8 = 2-7/8" | 29OMNIA23, 3,050 lm | 6.30" |
Length is the maximum overall length (MOL) in Westinghouse’s 2022 catalog. Other bulbs with the same code are longer or shorter.
Brightness
The shape doesn’t set the brightness: GE sells a 100 watt replacement giving 1,600 lumens as an A19 and as an A21. The bigger glass also carries brighter bulbs: 3,050 lumens from Feit’s OM200/830/LED A21 and Westinghouse’s A23.
| Bulb | Watts | Lumens | Length |
|---|---|---|---|
| GE A19, 100 W replacement | 15 | 1,600 | 4.65" |
| GE A21, 100 W replacement | 13.5 | 1,600 | 5.20" |
| GE A21, 200 W replacement | 21 | 2,900 | 5.71" |
| Feit A21, OM100DM/5CCTCA/LED/6 | 17.5 | 1,600 | 4.8" |
| Feit A21, OM150DM/CL/830/FIL | 18 | 2,605 | 5.3" |
| Feit A21, OM200/830/LED | 25 | 3,050 | 5.6" |
| Westinghouse A19, 15OMNIA19 | 15 | 1,600 | 4.92" |
The GE bulbs are its Refresh HD and Ultra Bright lines. Watts are the power each LED uses. Lengths from GE’s and Feit’s product pages and Westinghouse’s catalog.
Will an A21 fit?
- Lamps and shades. An A21 is taller and wider than an A19, so check that the shade, harp or glass has room for it.
- Garage door openers. Chamberlain’s openers take A19-size bulbs no more than 2.375" across, narrower than an A21. See garage door opener bulbs.
- Closed glass fixtures. Pick one rated for enclosed fixtures, because not every A21 is. Feit’s 28 watt OM150DM/830/LED isn’t, while its 18 watt OM150DM/CL/830/FIL, just as bright, is.
- The fixture’s limit. Compare the bulb’s Energy Used with the most watts the fixture allows: see fixture max wattage.
The base
The A19s and A21s in the tables all have the standard E26 base. GE notes that A shapes also come on the E12 candelabra base, so match the old bulb’s base as well as its size. 3-way A21s and A19s are on 3-way bulbs.
Turn the lamp or fixture off and let the old bulb cool before you take it out.
Another shape?
Bases and shapes