What is Mid-Side (M/S) processing?

Mid-Side is a stereo encoding technique that separates a stereo signal into a Mid channel (the mono sum: L+R) and a Side channel (the stereo difference: L-R). This lets you independently process the center and stereo-width content of a mix.

What are the M/S matrix equations?

To encode: M = (L + R) / 2, S = (L - R) / 2. To decode back: L = M + S, R = M - S. This tool applies both directions so you can convert freely between the two representations.

What does the stereo width percentage mean?

Stereo width is expressed as |S| / (|M| + |S|) × 100. A value of 0% means a fully mono signal (no side content). 50% means equal mid and side energy. 100% would mean no center content at all — a fully out-of-phase signal.

Should I use linear or dBFS values?

Use linear (0.0–1.0) for the M/S matrix math — amplitude arithmetic is only valid in linear scale. The dBFS inputs are converted to linear internally before calculation. Results are shown in both units.

Why does my mono mix show Side = 0?

A perfect mono signal has identical left and right channels. Since S = (L - R) / 2, if L equals R the side channel is exactly zero — which is correct behavior and means the signal is 100% mono-compatible.

Is this tool accurate for professional mastering?

Yes for amplitude-level calculations. Real-world M/S processing also involves time-domain phase relationships across the full frequency spectrum, which require an analyzer plugin in a DAW. This tool handles the scalar math that underpins those calculations.

Mid-Side Balance Calculator

Name: Mid-Side Balance Calculator
Availability: InStock
Author: Nham Vu

Convert between Mid/Side and Left/Right stereo signals, and calculate M/S balance ratios for mastering and audio production.

Input Values

Input unit:

Left (L)

Right (R)

Conversion Result

Enter values and click Calculate to see results.

M/S Width Reference

Width %	M/S Ratio	Perceived Character
0%	∞ : 0	Fully mono — no stereo width
10–20%	~4:1 – 9:1	Narrow — typical broadcast
25–35%	~2:1 – 3:1	Moderate — rock, pop mixes
40–50%	~1:1 – 3:2	Wide — electronic, ambient
> 60%	< 2:3	Very wide — check mono compatibility
100%	0 : ∞	No center — fully out-of-phase

Summary

Convert between Mid/Side and Left/Right stereo signals, and calculate M/S balance ratios for mastering and audio production.

How it works

Choose whether to start from L/R values or M/S values using the mode tabs.
Enter the amplitude values (in linear scale or dBFS) for both channels.
The tool applies the M/S matrix equations to compute the opposite representation.
Review the balance ratio and stereo width percentage in the results panel.
Use the reference table to understand how different M/S ratios affect perceived stereo width.

Use cases

Verify M/S encoder/decoder output during mastering sessions.
Calculate the mid and side levels from a known stereo balance.
Understand how much side content contributes to stereo width.
Check M/S ratios when preparing stems for broadcast (mono-compatible mixes).
Teach M/S processing concepts in audio engineering courses.
Troubleshoot phase issues by examining mid vs. side energy.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu