Choose the Right Base
Step 1 · Make sure your bulb fits
Before you decide on shape, color, or brightness, confirm the socket size in your fixture. A bulb with the wrong base simply won’t fit.
1. Inspect the socket. Does it look like a normal screw-in size, a tiny candle socket, or a two-prong twist-lock?
2. Match the base family. Pick the card below that matches what you see.
3. Choose bulbs from that base type. Once you know the base, every bulb you buy for that fixture must use it.
Common Bulb Bases and Where They’re Used
Standard Medium Base (E26)
The default screw-in base used in most US fixtures.
Typical fixtures
- Table lamps and floor lamps
- Ceiling domes and flush mounts
- Pendant lights
- Most outdoor fixtures
How to decide
- If the fixture looks like it would take a normal household bulb, this is almost always E26.
- A19, BR30, G25, and most common shapes use E26.
Candelabra Base (E12)
Narrow screw base found in decorative fixtures.
Typical fixtures
- Chandeliers
- Sconces with visible candle bulbs
- Some ceiling fans
- Decorative pendants
How to decide
- If the bulb is small and candle-shaped, you are most likely dealing with E12.
- B10/B11 bulbs almost always require E12.
Twist-Lock Base (GU10)
Short, twist-to-lock style used in directional spotlights.
Typical fixtures
- Track lighting
- Kitchen spotlight cans
- Accent lighting for artwork
How to decide
- If the bulb has two little nubs instead of threads, it is likely GU10.
- These aim light more narrowly than BR or PAR bulbs.
Quick base reference
Most fixtures
E26 medium base
Chandeliers
E12 candelabra
Spotlights
GU10 twist-lock
After you confirm the base, you’re ready to match your bulb shape.