A19 vs A21
Both use the same E26/E27 base and both are standard pear-shaped household bulbs, but A21 is 0.25 inches wider and roughly 0.75 inches longer.
Side-by-side specs
| Spec | A19 | A21 |
|---|---|---|
| Max diameter | 2.375 in (60 mm) | 2.625 in (67 mm) |
| Length (approx) | 4.13 in (105 mm) | 5.0 in (127 mm) |
| Base | E26 / E27 | E26 / E27 |
| Typical lumen range | 450–1100 lm | 1100–1600 lm |
View on Amazon | View on Amazon
Can you substitute one for the other?
Electrically yes, physically sometimes. A21 will not fit inside any shade or globe designed for A19 maximum width. In open fixtures with no enclosure, either works.