Is your amp under-powered, a good match or too much for your subs? RMS per sub, number of subs and amp RMS at the final load.
Sub RMS power, each (W)
The RMS (continuous) rating, not peak or max.
Number of subs
1
2
3
4
1
2
3
4
Amp RMS at your final load (W)
At the load you wire to (Sub wiring gives it).
Verdict
Good match (125 %)
Subs can take (RMS total)
800 W
Power per sub
1,000 W
Amp RMS that matches
600 W – 1,200 W
Tip
Set the gain with a test tone or meter, not by ear.
Guidance only, never a safety rating. Follow your amp and vehicle manuals. The fuse protects the wire: put it within 18 in of the battery. Disconnect the battery before you wire.
How it works
Enter the RMS rating of one sub, how many subs, and the amp’s RMS power at the load you wire to. The calculator compares them and says whether the amp is under-powered, a good match or over-powered.
Example: two 500 W RMS subs can take 1,000 W together. An amp making 1,000 W RMS at the final load is a 100 % match, 500 W per sub. 600 W is only 60 %: under-powered.
A good match runs from 750 to 1,500 W RMS for those two subs. Past 1,500 W you are over-powered and the gain has to be set with care.
Frequently asked questions
How many watts amp do I need for two 500 watt subs?
About 750 to 1,500 W RMS at the final load, with 1,000 W RMS right on the money.
Is it better to over-power or under-power a sub?
A bit more clean power is safer than a small amp pushed into clipping. Either way, the gain setting decides what reaches the sub.
Should I use peak or RMS power?
RMS. It is the continuous rating; peak or max numbers are not comparable between brands.