How much more power does a car amp make at 1, 2 and 4 ohm?

Short answer from the data: less than the textbook "doubles every time the load is halved". Across the 21 amps with a confirmed measurement at both 4Ω and 2Ω, the 2Ω result was a median of 1.89× the 4Ω result (lowest 1.53×, highest 2.13×). From 2Ω down to 1Ω it was a median of 1.50× across 19 amps, and from 4Ω to 1Ω a median of 3.04× across 15 amps.

Every amp with two or more confirmed loads

27 of our 44 amps have confirmed watts at two or more loads. Click an amp for its full results page and the source video.

Why isn't it exactly double?

For a fixed output voltage, power is voltage squared divided by impedance, so halving the load would double the power. Real amplifiers can't hold their output voltage at lower impedances: the power supply, the battery and wiring feeding it, protection circuits and the amp's own design limit how much current it can deliver. Those are general electrical reasons and aren't measured on this page, which only reports what each tester's dyno showed. It also means an amp's rating at one load tells you little about another, so compare amps at the load you will actually run (the impedance calculator works out your final load).

Method and limits

• Source: only numbers confirmed in each tester's public video text (title, description, chapters, pinned comment or captions), as on every AmpDyno amp page. Nothing here is estimated or interpolated. Where a load wasn't confirmed, the amp is simply left out of that ratio.
• Credit: measurements by TeamDroppinHz, Unofficial Audio, Williston Audio Labs. Each row links to the tester's video.
• Verification: amps marked "partial" on their pages have only some loads confirmed. They are included here only for the loads that were.
• Small, uneven sample: 44 amps from 5 testers, using different dynos, voltages and unit conditions. Treat the medians as a reality check on "it should double", not a prediction for a particular amp.
• Ratios, not ratings: this page compares an amp with itself at different loads. For box rating vs measured output see rated vs actual.

Next: most powerful amps at 1Ω · at 2Ω · at 4Ω · match an amp to your subwoofer.

Data from public dyno-test videos; each amp cites the tester and video. Results vary with voltage, unit and test setup.

Work on cars too? Check out the Tech Survival Guide, written by AmpDyno's founder, a working auto tech.