Posted by Yongtao Yu
on January 27, 2026
TL;DR — Quick Answer
- A19 / ST19 / G25 / B11 = bulb shape (how it looks and where it’s used).
- The number (like 19 in A19/ST19) is the diameter in eighths of an inch. A19 = 19/8" ≈ 2.375".
- E26 vs E12 = base size (socket fit). E26 is standard; E12 is candelabra.
Navigating the world of light bulbs can feel like learning a secret code. With names like A19, ST19, and G25—and bases like E26 or E12—it’s easy to get confused. This guide demystifies bulb shapes, sizes, and bases so you can choose the right bulb the first time (and avoid returns).
Light Bulb Shapes & Sizes at a Glance
| Type | What it looks like | Diameter | Common uses | Common base |
|---|---|---|---|---|
| A19 | Classic everyday bulb shape | 19/8" ≈ 2.375" | Ceiling lights, table lamps, enclosed fixtures | E26 |
| ST19 | Vintage Edison tubular look | 19/8" ≈ 2.375" | Decor pendants, vintage fixtures | E26 |
| G25 | Round globe bulb | 25/8" ≈ 3.125" | Bathroom vanities, decorative fixtures | E26 |
| B11 / BA11 | Candle-shaped decorative bulb | 11/8" ≈ 1.375" | Chandeliers, wall sconces | E12 |
Decoding Light Bulb Shapes: What Do the Letters Mean?
1) A19 — The Classic Everyday Bulb
- Size: 19/8" ≈ 2.375".
- Best for: Ceiling fixtures, table & floor lamps, enclosed fixtures.
2) ST19 — The Vintage Edison Look
- Elongated vintage aesthetic great for exposed pendants, chandeliers, and rustic décor.
3) G25 — The Globe Bulb
- Perfect for bathroom vanities and decorative visible fixtures with even light distribution.
4) B11 / BA11 — Decorative Candle Bulbs
- Decorative candle shape ideal for chandeliers and classic wall sconces.
Understanding Light Bulb Bases
E26 Base — Standard Medium
- The most common base in North America. Found on A19, ST19, and G25 bulbs.
E12 Base — Candelabra
- Smaller base typically found on B11 and BA11 decorative bulbs.
Shop by Shape — LafoHome Picks
Explore our most popular collections by bulb shape:
- A19 Everyday LED Bulbs Collection
- B11 Candle & Decorative Bulbs Collection
- ST19 Vintage Edison Bulbs Collection
- G25 Globe Bulbs Collection
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Bulb Size & Base FAQ
1) What does A19 mean?
A19 means a shape type “A” with a diameter of 19/8 inches.
2) Are A19 and ST19 the same size?
They often share diameter (19/8") but ST19 has a different silhouette for decorative use.
3) What does G25 mean?
G means globe, and 25 indicates a larger spherical diameter.
4) How do I know if my fixture uses E26 or E12?
Check your old bulb base or fixture label — lamps typically use E26, chandeliers often use E12.
5) Can an E26 bulb fit an E12 socket?
No, they are different sizes and will not fit interchangeably.
6) Are decorative bulbs compatible with dimmers?
Most are dimmable with compatible LED dimmer switches, but check specifications.
7) Which bulb is best for visible exposed fixtures?
ST19 and G25 are great for visible decorative fixtures due to their shape.
8) What’s the easiest way to avoid buying the wrong bulb?
Match the bulb shape and base — photo your current bulb to confirm.
