Automotive Light Bulb Size Chart
Use this automotive light bulb size chart as a quick reference when identifying replacement bulbs for headlights, fog lights, turn signals, brake lights, parking lights, and interior lamps. Bulb numbers describe a standardized bulb family, but the correct size still depends on the vehicle, lamp position, housing design, and model year.
Always confirm the bulb number in the owner’s manual, the vehicle’s original bulb, or a reliable parts catalog before buying. The same vehicle can use different bulb sizes in different positions, and regional versions may not match.
Headlight and Fog Light Bulb Sizes
These are among the most common exterior forward-lighting bulb families. Some are used for low beam, high beam, daytime running lights, or fog lights, but their application varies by vehicle.
- H1: Single-filament halogen bulb, commonly used for one headlight beam or auxiliary lighting.
- H3: Halogen bulb with a wire lead, often found in fog and auxiliary lamps.
- H4 / 9003 / HB2: Dual-filament bulb that can provide both low and high beam from one bulb.
- H7: Single-filament halogen bulb used in many headlight and fog light applications.
- H8: Single-filament bulb commonly used for fog lights and other auxiliary lamps.
- H9: High-output single-filament bulb; it may require checking connector and housing compatibility.
- H11: Common single-filament bulb used for fog lights and headlights.
- H16: A bulb family used in some fog and daytime running light applications. Check the exact base and connector before substituting it for another H-series bulb.
- 9005 / HB3: Single-filament bulb frequently used for high beam or daytime running lights.
- 9006 / HB4: Single-filament bulb frequently used for low beam or fog lights.
- 9012 / HIR2: Single-filament halogen bulb used in selected headlight systems; it is not automatically interchangeable with 9005 or 9006.
- 880 / 881: Compact single-filament bulbs used in some fog, cornering, or auxiliary lamps.
- 9145 / H10: Single-filament bulb often used in fog lights or other forward auxiliary lighting.
Exterior Signal, Brake, and Tail Light Sizes
Exterior signal bulbs are often identified by a numerical designation. Two bulbs can look similar while having different locking tabs, contact arrangements, or filament configurations.
- 1156: Single-filament, single-contact bulb commonly used for turn signals, reverse lights, or other single-function lamps.
- 1157: Dual-filament, dual-function bulb commonly used for tail and brake lights or parking and turn signals.
- 3156: Single-filament bulb used in some turn signal, reverse, or other exterior applications.
- 3157: Dual-filament bulb commonly used for brake, tail, turn signal, or daytime running light functions.
- 3155: Similar to the 3157 family in appearance, but the contact and function can differ. Verify the original number.
- 7440: Single-filament wedge bulb commonly used for turn signals or reverse lights.
- 7443: Dual-filament wedge bulb commonly used for brake, tail, or turn signal functions.
- 7441: Single-filament wedge bulb used in selected exterior signal applications.
- 921: Single-filament wedge bulb commonly used for reverse lights and some interior or utility lamps.
- 912: Similar wedge-style family used in selected interior, license plate, or exterior applications. Confirm the original bulb number.
Parking, License Plate, and Interior Bulb Sizes
- 194 / 168 / 2825: Small wedge bulbs commonly used for parking lights, side markers, license plate lamps, and interior lighting. Output and dimensions can vary between related numbers.
- 158: Small wedge bulb used in some instrument, parking, or marker-light applications.
- 6418: Festoon-style bulb used in some interior, license plate, and luggage-area lamps.
- DE3175 / 31 mm, 36 mm, or 42 mm festoon: Cylindrical bulbs retained between two spring contacts. Measure the original bulb length before ordering.
- 74: Small miniature bulb often used for dashboard, switch, and instrument illumination.
How to Verify the Correct Bulb Size
Check the bulb number
Remove the bulb only after switching off the vehicle and allowing the lamp to cool. Look for a printed number on the glass, plastic base, or metal collar. If the number is missing or unreadable, compare the bulb’s base, connector, locking tabs, and filament count with the replacement listing.
Confirm the lamp position
Do not assume that the high and low beams use the same bulb. Check each position separately, including fog lights, daytime running lights, front turn signals, rear turn signals, brake lights, reverse lights, and license plate lamps.
Check fitment before choosing LED
LED replacements may be sold as equivalents to halogen bulb numbers, but physical fit does not guarantee correct performance. Confirm polarity, heat management, beam pattern, dimming behavior, turn-signal flash rate, and dashboard-error compatibility. Some vehicles require a load resistor, decoder, or vehicle-specific LED design.
Installation Tips
- Compare the new bulb with the old one before installation.
- Keep halogen glass clean; handle it with gloves or a clean cloth.
- Seat the bulb fully and lock the connector or retaining spring.
- Test all lighting functions after installation.
- Replace bulbs in pairs when matching headlight color and brightness matters.
This chart is a starting reference, not a substitute for vehicle-specific verification. The original bulb number and the vehicle manufacturer’s lighting information should take priority.