What is the equilateral triangle rule for monitors?

Place the two monitors and your head at the corners of an equilateral triangle, so the distance between the two tweeters equals the distance from each monitor to your ears. Each monitor is angled 30° inward (toe-in) so it points directly at the listening position, giving a stable, centred stereo image.

How much should I toe-in my monitors?

For an equilateral setup each monitor toes in 30° from straight ahead, aiming directly at the listener. This puts you on-axis where the frequency response is flattest and narrows the sweet spot. Some engineers reduce toe-in slightly to widen the image; experiment, but 30° is the standard starting point.

What is the 38% rule?

The 38% rule places the listening position about 38% of the room length back from the front wall. At that point the listener tends to avoid the worst pressure peaks of the room's length-wise axial modes, giving smoother bass. It is a starting guideline, not an absolute — fine-tune by ear and with measurement.

How far should monitors be from the walls?

Keep monitors away from the front and side walls — at least roughly half a metre where the room allows — to reduce boundary reinforcement and speaker-boundary interference (SBIR) that causes bass dips. Avoid placing a monitor the same distance from the front wall as from the side wall, which stacks reflections at similar frequencies.

Should monitors fire down the long or short wall?

Firing down the longer dimension of the room generally gives more even bass and pushes the strongest front-to-back reflection further away, but it costs floor space. If the room is wide, firing across the short dimension can work with careful side-wall treatment. The calculator uses your stated length as the firing axis.

Studio Monitor Placement Calculator

Where you put your studio monitors matters as much as which monitors you buy. A correct equilateral triangle, the right toe-in, a smart listening position, and sensible distances from the walls turn an average room into a reliable mixing environment. This calculator takes your room dimensions and desired monitor separation and returns the full placement geometry.

How it works

The core of nearfield monitoring is the equilateral triangle: the two tweeters and your head sit at the corners of a triangle whose sides are all equal. So the listening distance is set equal to the monitor separation, and each speaker toes in 30° so it points straight at your ears:

listening distance = tweeter-to-tweeter separation

The listening position uses the 38% rule: place your head about 38% of the room length back from the front wall to dodge the worst length-wise room-mode pressure peaks:

listener from front wall = 0.38 × room length

The speakers sit one triangle height in front of you. For an equilateral triangle of side s, that height is:

triangle height = (√3 / 2) × s

so the speaker distance from the front wall is listener from front − triangle height, and each speaker is offset s/2 either side of the room centreline.

Example

In a 5 m × 3.6 m room with 1.5 m separation:

Listening distance: 1.5 m to each monitor, 30° toe-in
Listener from front wall: 0.38 × 5 = 1.9 m
Triangle height: 0.866 × 1.5 ≈ 1.3 m, so speakers ≈ 0.6 m from the front wall
Each speaker ≈ 0.75 m from the centreline, ≈ 1.05 m from the nearest side wall

Notes

Set the tweeters at ear height and keep the setup symmetric left-to-right so reflections arrive equally on both sides. The 38% and equilateral guidelines get you a strong starting point, but always confirm with your ears and, ideally, a measurement microphone — treat the first reflection points on the side walls and ceiling, and keep the monitors clear of the walls to tame bass. All calculations run locally in your browser.