1156 vs 1157 LED Bulb: What's the Difference and Which Do You Need?

1156 vs 1157 LED Bulb: What's the Difference and Which Do You Need?

If you've ever tried to replace a brake light, turn signal, or reverse light on your car, you've likely come across the numbers 1156 and 1157. These are two of the most common automotive bulb standards in North America, and while they look similar at first glance, they are fundamentally different — and not interchangeable.

This guide explains exactly what separates the 1156 from the 1157, which applications each one is used for, and how to make sure you order the right LED replacement.

The Core Difference: Single Filament vs. Dual Filament

The most important difference between the 1156 and 1157 is the number of filaments:

● 1156 (BA15S) — Single filament, single contact base. One brightness level, one function.

● 1157 (BAY15D) — Dual filament, dual contact base. Two brightness levels, two functions simultaneously (e.g., tail light + brake light).

You can also identify them by the base pins: the 1156 has two pins at the same height, while the 1157 has two pins at different heights (offset). This prevents a 1157 from being inserted into a 1156 socket and vice versa.

Common Applications

1156 (single filament) is used for:

● Rear turn signals (single function — flash only)

● Reverse/backup lights

● Front turn signals on some vehicles

● Side marker lights

1157 (dual filament) is used for:

● Combination brake and tail lights (dim when parked, bright when braking)

● Front parking and turn signal combinations

● Rear combination lamp assemblies on trucks and SUVs

How to Identify Which One Your Vehicle Needs

The easiest way is to remove the existing bulb and look at the number printed on the glass or base. If the number is worn off, look at the base:

● Two equal-height pins → 1156 (BA15S)

● Two unequal-height pins → 1157 (BAY15D)

Choosing an LED Replacement

For 1156 LED replacement: Look for BA15S base LEDs in the appropriate color (amber for turn signals, white for reverse lights, red for brake/tail).

For 1157 LED replacement: The LED must support dual-brightness operation. Look for BAY15D dual-contact LED bulbs. If your vehicle detects LED load, choose a canbus-compatible version to avoid dashboard warning lights.

Do You Need a Load Resistor?

Many modern vehicles monitor the current draw of each bulb. When you replace a 1156 or 1157 incandescent bulb with an LED, the lower current draw may cause hyperflashing (turn signals flashing too fast) or a dashboard warning light.

Solutions:

1. Choose a canbus error-free LED with built-in load resistor

2. Install an external load resistor in parallel with the LED

Zhishan offers both standard and canbus-compatible versions of 1156 and 1157 LED bulbs in white, amber, and red. 

View the full 1156/1157 LED range: https://www.carsledbulb.com/1156-1157-led/ 

Need help selecting the right bulb for your vehicle? Contact our team — we respond within 24 hours: https://www.carsledbulb.com/about-us/