Lamp Holder & Bulb Cap Sizes: E27 vs E26 vs B22, explained.
Every bulb attaches by a cap (base), and every fixture has a matching holder (socket). Get the code right and the bulb fits; get it wrong and nothing seats. This guide is the full chart — screw caps (E27, E26, E14), bayonet caps (B22, B15) and pin types — plus the one that confuses everyone: is E26 the same as E27?
Bulb cap & holder size chart.
The cap code reads as a letter + a number: the letter is the type (E = Edison screw, B = bayonet, G/GU = pin), and the number is the diameter or pin spacing in millimetres. Here are the codes you’ll actually meet.
| Cap code | Name | Diameter | Region / typical use |
|---|---|---|---|
| E27 | Edison Screw (ES) | 27 mm | Europe, UK, Asia — the world standard |
| E26 | Medium Edison (MES) | 26 mm | North America (120V) standard |
| E14 | Small Edison (SES) | 14 mm | Europe — candle, fridge & accent bulbs |
| E12 | Candelabra (CES) | 12 mm | North America — chandelier / candle |
| E40 | Goliath Edison (GES) | 40 mm | Industrial / high-bay / street lighting |
| E39 | Mogul | 39 mm | North America industrial / high-wattage |
| B22 | Bayonet Cap (BC) | 22 mm | UK & Commonwealth — push & twist |
| B15 | Small Bayonet (SBC) | 15 mm | UK — candle & small fittings |
| GU10 | Twist-lock spot | 10 mm pin gap | Mains spotlights / downlights |
| G9 / G4 | Bi-pin | 9 / 4 mm pin gap | Capsule bulbs, decorative fittings |
Most table, floor and pendant lamps use E27 (or E26 in North America); chandeliers and wall lights use E14 / E12 or B15; UK fittings often use B22. Need the shade, not the bulb? See the lamp shade size & fitter guide.
E27 vs E26 — are they the same?
Mechanically, the 1 mm gap is small enough that an E26 bulb will usually screw into an E27 holder and vice-versa. For a one-off bulb swap, they’re effectively cross-compatible.
Electrically is what matters. E27 fittings are wired for 220–240V (Europe, UK, most of Asia); E26 fittings for 110–120V (North America). Putting a 120V bulb on 230V mains will blow it instantly — and the reverse runs dim. Always buy the bulb rated for your region’s voltage.
The Edison screw family.
Screw caps thread in. Named after Edison, coded “E” + diameter in mm. These five cover almost every screw-fit bulb you’ll meet.
Edison Screw (ES)
27 mm. The global standard for table, floor & pendant lamps.
Medium Edison
26 mm. The North American 120V equivalent of E27.
Small Edison (SES)
14 mm. Candle, accent & appliance bulbs in Europe.
Candelabra (CES)
12 mm. The US chandelier / candle base.
Goliath (GES)
40 mm. Industrial high-bay, street & flood lighting.
Mogul
39 mm. North American high-wattage industrial base.
Bayonet caps: push & twist.
Common in the UK and former Commonwealth, bayonet caps don’t thread — two pins lock into the holder with a quarter turn. Coded “B” + diameter.
| Cap code | Name | Diameter | Typical use |
|---|---|---|---|
| B22 | Bayonet Cap (BC) | 22 mm | UK standard for table, floor & ceiling fittings |
| B15 | Small Bayonet (SBC) | 15 mm | UK candle bulbs, small & appliance fittings |
| BA15d / BA9s | Miniature bayonet | 15 / 9 mm | Automotive, indicator & signal lamps |
Pin & twist-lock bases.
Spotlights and capsule bulbs use pins instead of a cap. Coded “G” (the number is the gap between pins in mm); “U” means twist-lock.
Twist-lock spot
10 mm pin spacing, mains voltage. Push and twist — the standard for downlights and track spots.
Bi-pin capsule
9 mm loop pins, mains voltage. Small decorative fittings, wall lights and some pendants.
Low-voltage capsule
4 / 5.3 mm pins, 12V (needs a transformer/driver). Under-cabinet and accent lighting.
How to identify your holder in 10 seconds.
Look at the old bulb — its base tells you everything.
It screws in
That’s an Edison cap. Measure the base diameter: ~27 mm = E27, ~26 mm = E26, ~14 mm = E14, ~12 mm = E12.
It pushes & twists
Two pins on the side = bayonet. ~22 mm across = B22, ~15 mm = B15.
It has thin pins
Two prongs sticking out = pin type. Wide twist = GU10; thin loops ~9 mm = G9; tiny ~4 mm = G4.
Holder size vs shade fitter.
If you’re sourcing a glass shade, you need its fitter spec, not just the bulb holder. On a glass pendant the shade has its own fitter neck (1-5/8″, 2-1/4″, 3-1/4″, 4″) that’s independent of whether the bulb is E27 or B22. On a European ring-fit shade, the shade ring sits over the E27/B22 holder, so the holder size does matter.
Lamp Shade Sizes & Fitters
How to measure a shade and the four fitter systems — spider, uno, clip-on and glass neck.
Open the size guide →
Lamp Shade Shapes
Globe, dome, drum, empire, bell and more — the visual glossary of shade silhouettes.
See shade shapes →
Shades Made to Fit
Tell us your holder and fitter — we make the glass to match, in volume.
Start a custom shade →
Glass shades made to fit any holder.
If you build or source lighting, the holder is your spec — the glass should fit it, not the other way round. As a glass lampshade manufacturer we neck and drill shades for E27, E26, B22, E14 and bespoke holders, and ship the same fixture spec’d differently for each market.
| Spec | Capability |
|---|---|
| Holder compatibility | E27 · E26 · E14 · E12 · B22 · B15 · E40 · GU10 fittings |
| Fitter necks | 1-5/8″, 2-1/4″, 3-1/4″, 4″ · any custom neck to drawing |
| Glass & finish | Clear · opal/white · frosted · amber · borosilicate · custom tint |
| MOQ | 500 pcs per SKU (250-pc trial negotiable) |
| Certifications | CE · RoHS · REACH · SMETA · ISO 9001:2015 |
Related reference guides.
Lamp holder & bulb cap FAQs.
What is the difference between E27 and E26 bulbs?
Both are medium Edison screw caps and look almost identical. E27 is 27 mm (Europe, UK, Asia — 230V); E26 is 26 mm (North America — 120V). The 1 mm difference usually lets them thread together, but match the bulb’s voltage to your supply. See the comparison →
Are E26 and E27 interchangeable?
Mechanically, mostly yes — the 1 mm gap usually lets an E26 bulb thread into an E27 holder and vice-versa. Electrically you must match the voltage: 120V bulbs on 120V supply, 220–240V bulbs on 230V supply. For permanent, certified fixtures, use the holder and bulb rated for your region.
What does E27 mean?
“E” is for Edison (a screw-type cap) and “27” is the thread diameter in millimetres. So E27 = a 27 mm Edison screw cap — the most common bulb base in the world outside North America.
What is a B22 bayonet cap?
B22 (BC, bayonet cap) is a 22 mm push-and-twist base used mainly in the UK and former Commonwealth. Two pins lock into the holder with a quarter turn instead of threading. The small version is B15 (SBC).
How do I know what bulb holder I have?
Check how the old bulb attaches. Screws in = Edison (≈27 mm = E27, 26 mm = E26, 14 mm = E14). Push & twist with two pins = bayonet (≈22 mm = B22, 15 mm = B15). Thin pins = GU/G type. The code is usually printed on the old bulb too. See the diagnosis guide →
Does the bulb holder affect which lamp shade fits?
Indirectly. The holder determines the bulb; a separate fitter (spider/harp, ring, or glass fitter neck) holds the shade. On many European fittings a ring shade sits on the holder, so the holder size matters; on glass pendants the shade has its own fitter neck independent of the bulb. Confirm both — see the shade size & fitter guide.
Tell us the holder — we’ll make the glass to fit.
E27, E26, B22 or a bespoke base, in clear, opal or borosilicate: send your holder and fitter spec and we’ll quote in 24 hours. Glass lampshade manufacturer since 1999, shipping to 150+ countries.