H4 Bulb vs. H7 Bulb
Comparing 2 standards across 11 specifications. 11 key differences identified.
The H4 Bulb (marketed as 9003 or HB2 in North America under DOT regulations, standardized with a P43t 3-prong base) is the legendary dual-filament automotive headlight bulb. Containing both a 55W low-beam filament (equipped with an internal stamped metal anti-glare shield cup) and a 60W high-beam filament inside a single halogen quartz glass capsule.
The H7 Bulb (standardized under UN ECE Regulation 37 with a PX26d flanged base) is the most widely used single-filament halogen automotive headlight bulb in the world. Operating at 55W nominal at 12V (rated at 13.2V test voltage), it generates 1,500 lumens (±10%) primarily for low-beam projector and reflector headlight assemblies.
Specification Comparison Table
11 Parameters| Parameter / Spec | ||
|---|---|---|
|
Standardization
|
UN ECE R37 (H4) / US DOT FMVSS 108 (HB2 / 9003) / IEC 60061-1 | UN ECE R37 Category H7 / IEC 60061-1 sheet 7004-5 / US DOT Category H7 |
|
Base Socket Designation
|
P43t (3 large radial metal locating tabs with 3 heavy electrical blade terminals) | PX26d (pre-focused metal circular mounting flange with one flat reference indexing tab) |
|
Luminous Flux Output
|
Low Beam: 1,000 lumens ± 15% | High Beam: 1,650 lumens ± 15% (at 13.2 V) | 1,500 lumens ± 10% (at 13.2 V) |
|
Filament Architecture
|
Dual tungsten filaments: Low Beam (55W) + High Beam (60W) | — |
|
Internal Anti-Glare Shield
|
Stamped nickel cup positioned under the low-beam filament blocks downward light, creating a crisp horizontal beam cutoff | — |
|
Electrical Connector
|
3-prong female socket (Ground, Low Beam 12V+, High Beam 12V+) | — |
|
Application Domain
|
Standard in motorcycles (single headlight unit), compact hatchbacks, classic 7-inch round sealed-beam replacements | — |
|
Filament Type
|
— | Single axial tungsten filament (no internal shield; strictly a single-beam bulb) |
|
Nominal Power & Voltage
|
— | 55 W @ 12V nominal (tested at 13.2V standard regulation voltage; draws ~4.17 A) |
|
Average Lifespan (B3 / Tc)
|
— | B3 (97% survival): ~330 hours | Tc (63.2% failure): ~550 hours (standard halogen) |
|
Electrical Terminals
|
— | 2 spade push-on terminals (6.3 mm faston tabs spaced 14.5 mm apart) |