Light bulb size chart
A standard A19 bulb is 2 3/8 in (60 mm) across at its widest, and an E26 base is 26 mm across. Base codes give the size in mm; shape codes give the diameter in eighths of an inch.
Light bulb size chart: the tool
Bulb code decoder
The letter is the shape and the number is the widest diameter in eighths of an inch.
Bulb base size chart (screw and bayonet)
| Base | Name | Diameter | Where used |
|---|---|---|---|
| E5 | Lilliput Edison Screw (LES) | 5.5 mm | |
| E10 | Miniature Edison Screw (MES) | 10 mm | |
| E11 | Mini-candelabra | 11 mm | |
| E12 | Candelabra (CES) | 12 mm | North America: chandeliers, decorative lamps |
| E14 | Small Edison Screw (SES) | 14 mm | Europe and most 220 to 240 V countries |
| E17 | Intermediate (IES) | 17 mm | North America |
| E26 | Medium Edison Screw | 26 mm | North America standard household (A19 bulbs usually have E26, per Wikipedia A-series) |
| E27 | Edison Screw (ES) | 27 mm | Europe and most of the world standard household |
| E39 | Mogul | 39 mm | North America high-wattage |
| E40 | Goliath (GES) | 40 mm | Europe high-wattage |
| B22d | Bayonet cap (BC) | 22 mm | UK, Australia, India, Ireland, New Zealand, Hong Kong, parts of the Middle East and Africa |
| BA15d | Small bayonet cap (SBC) | 15 mm |
Pin bases (GU10, GU24, G9, MR16)
| Base | Pin spacing | Pin diameter | Typical use |
|---|---|---|---|
| G4 | 4 mm | 0.65 to 0.75 mm | small halogen capsules, 6/12 V |
| GU4 | 4 mm | 0.95 to 1.05 mm | MR11, MR8 |
| GU5.3 | 5.33 mm | 1.45 to 1.6 mm | MR16 low-voltage (12/24 V) |
| GY6.35 | 6.35 mm | 0.95 to 1.05 mm | halogen, task and landscape lighting |
| G9 | 9 mm | halogen and LED capsules, 120 V (US) / 230 V (EU) | |
| GU10 | 10 mm | 5 mm | twist-lock mains MR16-size spots (120/230 V) |
| G13 | 12.7 mm | 2.35 mm | T8, T10, T12 fluorescent tubes |
| GU24 | 24 mm | twist-lock compact fluorescent and LED | |
| GX53 | 53 mm | twist-lock puck lamps |
Bulb shape size chart
| Code | Shape | Diameter | Basis |
|---|---|---|---|
| A15 | standard (arbitrary) | 1.875 in (48 mm) | stated |
| A19 | standard (arbitrary) | 2.375 in (60 mm) | stated |
| A21 | standard (arbitrary) | 2.625 in (66.7 mm) | stated (in); mm by conversion |
| A23 | standard (arbitrary) | 2.875 in (73 mm) | stated (in); mm by conversion |
| B11 | blunt tip / torpedo candle | 1.375 in (34.9 mm) | eighths rule |
| C7 | candle / Christmas light | 0.875 in (22.2 mm) | eighths rule |
| C9 | candle / Christmas light | 1.125 in (28.6 mm) | eighths rule |
| G25 | globe | 3.125 in (79.4 mm) | eighths rule |
| G30 | globe | 3.75 in (95.3 mm) | eighths rule |
| ST19 | straight-tapered (vintage Edison look) | 2.375 in (60.3 mm) | eighths rule |
| R20 | reflector | 2.5 in (63.5 mm) | stated (in); mm by conversion |
| BR20 | bulged reflector | 2.5 in (63.5 mm) | stated (in); mm by conversion |
| BR30 | bulged reflector | 3.75 in (95.3 mm) | stated (in); mm by conversion |
| BR38 | bulged reflector | 4.75 in (120.7 mm) | stated (in); mm by conversion |
| BR40 | bulged reflector | 5 in (127 mm) | stated (in); mm by conversion |
| MR16 | multifaceted reflector | 2 in (50.8 mm) | stated (in); mm by conversion |
| PAR20 | parabolic aluminized reflector | 2.5 in (63.5 mm) | stated (in); mm by conversion |
| PAR30 | parabolic aluminized reflector | 3.75 in (95.3 mm) | eighths rule |
| PAR38 | parabolic aluminized reflector | 4.75 in (120.7 mm) | eighths rule |
| T5 | tube | 0.625 in (15.9 mm) | eighths rule |
| T8 | tube | 1 in (25.4 mm) | stated (in); mm by conversion |
| T12 | tube | 1.5 in (38.1 mm) | stated (in); mm by conversion |
Good to know
- Base (cap) codes: the letter is the base family and the number is the diameter in mm for screw (E) and bayonet (B) bases, or the pin spacing in mm for pin bases (G, GU, GX). Base standard: IEC 60061 (cited by Wikipedia for both Edison screw and bi-pin bases).
- E26 (North America) and E27 (Europe and most of the world) are usually interchangeable; Wikipedia notes a 1 mm difference in thread diameter and a small difference in pitch.
- Shape codes: the letter is the shape, the number is the diameter at the widest point in eighths of an inch (A19 = 19/8 in = 2 3/8 in). ENERGY STAR's Lamps V2.1 specification states 'lamp diameter in eighths of an inch (e.g., MR-16 diameter = 16 eighths of an inch)' and names ANSI C79.1-2002 as the shape designation standard. Outside North America the A number is in mm (A60 is the A19 equivalent, per Wikipedia).
Related tools
Planning a lighting project? Recessed lighting cost.
Questions
Are E26 and E27 bulbs the same?
They are usually interchangeable: E26 is the North American medium base and E27 the European one, about 1 mm apart in thread diameter (Wikipedia).
What does A19 mean?
A is the classic bulb shape and 19 is the widest diameter in eighths of an inch: 19/8 = 2 3/8 in, about 60 mm.
What size is a candelabra base?
E12, 12 mm across, used in chandeliers and decorative lamps in North America.
Sources
- Wikipedia: Edison screw (checked 2026-10-05)
- Wikipedia: Bi-pin lamp base (checked 2026-10-05)
- Wikipedia: Bayonet mount (checked 2026-10-05)
- US EPA ENERGY STAR: ENERGY STAR Program Requirements for Lamps V2.1 (checked 2026-10-05)
- Wikipedia: A-series light bulb (checked 2026-10-05)
- 1000Bulbs: What Type of Light Bulb Is This? (checked 2026-10-05)
Last checked: 5 October 2026