Rex says
Everyday utility math — the kind you'd otherwise pull up four browser tabs for. I keep it to one clean answer.
Try a scenario
Click to load — tweak from there.Inputs
Result
Total peak system wattage needed
10,200
Continuous (RMS) power target
3,400
Watts per person used
17
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter expected attendees.
- 2Enter show type.
- 3Enter headroom multiplier for peaks.
- 4Read your total peak system wattage needed on the right — it updates as you type.
- 5Hit Share to keep the scenario or send it to someone.
About this calculator
Undersizing a PA leads to clipped, distorted sound at the volume a room actually needs, while oversizing wastes money on speakers you'll never push. A rough rule of thumb used by sound techs is roughly 10 watts of amplifier power per person for speech-level background music, 15-20 watts per person for live bands at moderate volume, and 20-30+ for loud rock/EDM shows, then adding 3-6 dB of headroom (which requires roughly 2-4x the continuous power rating) so peaks don't clip.
Worked example
Using the values the calculator loads with:
Inputs
- Expected attendees: 200
- Show type: Live band, moderate volume (~17 W/person)
- Headroom multiplier for peaks: 3
Results
- Total peak system wattage needed: 10,200
- Continuous (RMS) power target: 3,400
- Watts per person used: 17
What each field means
Inputs
- Expected attendees
- The expected attendees used in the calculation. Starts at 200 so you have a working example on load.
- Show type
- Pick the option that matches your situation — the maths changes per option. Choices: Background music / speech (~10 W/person), Live band, moderate volume (~17 W/person), Loud rock / EDM (~25 W/person).
- Headroom multiplier for peaks
- The headroom multiplier for peaks used in the calculation. Starts at 3 so you have a working example on load. Accepted range: 1–6.
Results
- Total peak system wattage needed
- Returned as a whole number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Continuous (RMS) power target
- Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Watts per person used
- Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
Why does peak power need to be 2-4x continuous power?
Music has a high crest factor — brief transient peaks (kick drum hits, snare cracks) run well above the average continuous level, and an amplifier that only just covers the average will clip hard on every transient. Headroom of 3-6 dB (roughly 2-4x power) keeps those peaks clean.
Does room type change this estimate?
Yes significantly — outdoor shows lose bass energy and overall level to open air and need more power than this indoor-oriented rule of thumb suggests, while small, reflective rooms need less because walls reinforce the sound. Treat this as a starting point, not a final spec, especially outdoors.
Is more wattage always louder?
No — speaker sensitivity (dB SPL at 1W/1m) affects loudness as much as amplifier wattage, and every doubling of power only adds about 3 dB of perceived loudness. A high-sensitivity speaker at 500W can outperform a low-sensitivity speaker at 1000W.
Accuracy and limitations
- Estimates assume standard, average conditions — local rules, pricing, and materials vary.
- Results are rounded for readability; add a buffer before ordering, booking, or committing.
- Double-check anything with a real cost attached against a local quote.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). PA Power/Wattage Sizing Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/pa-power-sizing
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/pa-power-sizing" target="_blank" rel="noopener">PA Power/Wattage Sizing Calculator — RevenueLab</a> (2026).</p>
Source: [PA Power/Wattage Sizing Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/pa-power-sizing) (2026).