Stereo Width Calculator
Calculate the stereo width ratio from mid-side (M/S) processing using mid and side channel gain values in dB. Use this when mixing or mastering to quantify how wide your stereo image is.
Last updated: October 2026
Width Factor
1.41
Formula below · 2 sources (soundonsound.com, csound.com) · Updated Oct 2026
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About this calculator
Stereo width in mid-side processing is the side level divided by the mid level as a linear ratio: raising the side channel 3 dB above the mid gives a width factor of about 1.41, and +6 dB gives about 2.0. The calculator converts each gain from decibels to linear amplitude with 10^(dB ÷ 20) and divides side by mid, so only the difference between the two gains matters.
Mid and side
Mid-side (M/S) processing re-expresses a left-right stereo signal as a mid channel, the sum of left and right, which holds everything common to both sides, and a side channel, the difference between them, which holds the stereo information. Converting to M/S and back is lossless, so you can change the balance between the two, or EQ and compress one without the other, and return to left-right stereo.
What the width factor means
A factor of 1.0 leaves the mix as it was. Above 1.0 the side signal is louder relative to the center, so reverbs, pads and panned parts spread out and the image sounds wider. Below 1.0 the image narrows, and at 0 (side muted) it is mono. The table below converts common gain differences.
Watch mono compatibility
When left and right are summed to mono, the side channel cancels completely. Anything you push into the sides by widening disappears on mono playback, such as phone speakers and some club systems, and the mid content then has to carry the mix. Check widened mixes in mono and on a correlation meter, where readings that drop toward or below zero warn of cancellation.
| Side minus mid (dB) | Width factor | Effect on the image |
|---|---|---|
| Side muted | 0 | Mono |
| −6 | 0.50 | Much narrower |
| −3 | 0.71 | Narrower |
| 0 | 1.00 | Unchanged |
| +1 | 1.12 | Slightly wider |
| +3 | 1.41 | Wider |
| +6 | 2.00 | Much wider; check mono |
How to use
Enter the gain applied to the mid channel and to the side channel in dB, as set on your M/S EQ, imager or encoder. The default, 0 dB mid and +3 dB side, gives a width factor of about 1.41. Equal gains always give 1.0; −6 dB on the sides with the mid at 0 gives about 0.50, a noticeably narrower image.
Frequently asked questions
What does a width factor of 1.0 mean?
The side and mid channels have their original relative level, so the stereo image is unchanged. Any equal change to both gains, such as −2 dB on each, also gives 1.0, because only the difference between them sets the width.
How much does each dB of side gain widen the mix?
Every 6 dB doubles the linear ratio: +6 dB on the sides relative to the mid gives about 2.0, and −6 dB gives about 0.5. Small changes of 1 to 3 dB (factors of about 1.12 to 1.41) are common in mastering, because large boosts can make the center sound weak.
Why does widening hurt mono compatibility?
In a mono sum the side signal cancels out, because it is the difference between left and right. Material that only exists in the sides vanishes in mono, so a heavily widened mix can lose reverb, backing parts or stereo effects on mono playback.
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