Free Calculator

Speaker SPL & Distance Calculator

How loud your speakers actually play at the chair, with all the physics dialled in: speaker sensitivity, amplifier wattage, distance, room boundary gain, and stereo pair summation. Drag the dot on the chart to set your seat and watch the SPL update live.

My rigs

Save speaker+amp+room setups here. Useful when you're swapping speakers or considering a new amp.

SPL at the chair - -
Vs your target - -
WHO safe time
- 85 dB / 8 h baseline with 3 dB exchange rule.

Your speakers

source
dB / W / m

Bookshelf: 84-88. Floor-stander: 87-92. Horn: 95+.

Your amp

drive
W

Clean RMS into the speaker's nominal impedance. Use 1 W to read the speaker's 1 m sensitivity directly.

Channel mode

Room & target

tune

Or drag the dot on the chart below to set this visually.

Room size (boundary gain)
dB
Target listening level
dB SPL

SPL falloff with distance

drag to set

Log distance axis - the inverse-square line comes out straight. Drag the dot to set your listening distance and watch every number above update live. The dashed orange line is your target SPL; where it crosses the curve is the seat position that hits your target exactly.

Show the math

How distance and room gain shape SPL at the chair

The inverse square law

In free space, doubling distance from a point source costs you 6 dB. A speaker at 86 dB/W/m drops to 80 dB at 2 m and 74 dB at 4 m. A cinema seat at 5 m needs about 14 dB more output than a nearfield chair at 1 m to hit the same level - that's a 25x power requirement, not a doubling. The chart's log x-axis makes the inverse-square line straight; if your curve isn't straight, the chart isn't honest.

Real rooms add room boundary gain: 6 dB in small treated spaces, 3 dB in typical furnished rooms, ~1 dB in large rooms. The room-size pills set sensible defaults; the custom field lets you trim for your actual space.

Stereo pair, headroom, and safe-listening time

A stereo pair sums about +3 dB at the chair (correlated content). Crest factor matters: the peak-SPL line is the average + 6 dB, so a 95 dB average reading means real-world peaks bumping 101 dB. Your amp has to deliver those peaks cleanly - clipping them spells driver damage faster than the peak SPL alone implies.

WHO safe-listening time uses the 85 dB / 8 h baseline with a 3 dB exchange rule: every +3 dB halves the safe duration. 95 dB at the chair = 47 min/day. 105 dB = 4.7 min/day. The safe-time pillar above tells you how long you can listen at the current SPL before crossing the daily-dose line.

SPL reference points, in things you've heard

Anchor numbers: what every dB level actually sounds like.

30 dBWhisper

Quiet bedroom at night. Noise floor of a treated room.

60 dBConversation

Normal speaking voice at a metre. Background office.

75 dBLate-night

Hi-fi at low volume. Neighbour-friendly.

85 dBCinema ref

Movie average. WHO long-term safe ceiling.

95 dBLoud music

Rock club at the bar. 47 min/day safe.

105 dBCinema peaks

Action sequence transients. Front-row arena.

115 dBLive concert

PA at full tilt. 30 s before daily dose blown.

130 dBPain

Jet engine at 30 m. Damage in seconds.

FAQ

Speaker SPL and distance FAQ.

How loud your speakers actually play at the chair, how much amp power you really need, and why spec-sheet sensitivity overstates the room reality.

  1. How loud will my speakers be at the listening position?

    Sound pressure drops 6 dB every time the listening distance doubles in a free field. Enter your speaker sensitivity (dB SPL/W/m), the amplifier wattage, and the chair distance. The calculator returns the SPL at your ears, accounting for inverse-square falloff plus a small room-gain correction below 200 Hz.

  2. How much amplifier power do I need for my speakers?

    For 88 dB/W/m speakers at 3 m wanting 100 dB peaks, you need around 100 W per channel. Halve the sensitivity (-3 dB) and you need double the power; double the distance and you need quadruple. The calculator handles all three variables and adds a 12 dB headroom factor for transients.

  3. What is speaker sensitivity in dB/W/m?

    Sensitivity is the SPL a speaker produces with 1 watt of input measured at 1 meter on-axis. 86 dB/W/m is below average; 88-91 dB is mainstream; 93+ is high-sensitivity (horn-loaded, large drivers). High sensitivity speakers need much less amplifier power for the same loudness.

  4. Why do my speakers sound quieter than the spec suggests?

    Spec sheet sensitivity is measured anechoic at 1 m on-axis. Your room adds bass gain but eats midrange via absorption and dispersion, and 1 m is closer than any real chair. The calculator uses 2 dB room-gain compensation and your real chair distance, which is closer to what you actually hear.

  5. How do I read the SPL falloff chart on this calculator?

    The x-axis is listening distance on a log scale, the y-axis is SPL in dB. The blue curve is the average SPL with room gain; the orange line above it is the +6 dB peak SPL for music transients; the dashed grey line at 85 dB is the WHO safe-exposure ceiling. The marker dot is where your current listening distance lands. Move the chair closer or further to see the curve update.

  6. Does the inverse-square law apply indoors?

    Partly. In the direct-sound near-field (typically within 1-2 m of the speaker indoors) sound drops 6 dB per doubling of distance just like free-field. Beyond the critical distance the reverberant field dominates and the level becomes nearly constant with distance. That is why a small treated room sounds louder at the back wall than physics would predict. The calculator models the inverse-square component plus a simple room-gain term; for full reverberant-field accuracy a measurement microphone is the answer.