Theater Calculators

Screens & projection

Projector Throw Distance Calculator

Throw ratio is lens-to-screen distance divided by image width. Use the manufacturer min/max, not a forum guess. Offset and lens shift still eat the window.

Inputs

Units
in

From the lens chart, distance / image width.

Results

Image width
2.66m
Minimum throw
3.59m
Maximum throw
5.84m
Mid-zoom throw
4.72m

Recommended gear

Calculation method

Width from the diagonal and aspect; throw = width × ratio. Mid-zoom is the average of the min and max ratios.

Exact formula

W from diagonal as in the aspect tool. d_min = W · r_min, d_max = W · r_max. Limits: ignores lens shift, zoom memory, keystone and UST bounce screens.

Throw ratio is width, never the diagonal

Manufacturers quote throw as lens-to-screen distance divided by image width. A 120-inch 16:9 screen is about 2.65 m wide, not 3.05 m on the diagonal. Entering the diagonal as width stretches the mount by about 15% and you drill the ceiling in the wrong bay.

Lens shift does not rewrite the zoom window

Vertical or horizontal shift barely changes throw ratio, but it can push you off the charted zoom range or into keystone. Ultra-short-throw ratios below 0.5 still use the same multiply; bounce ALR screens add their own offset from the wall. Confirm on the projector PDF before you cut a mount.

Frequently asked questions

Is throw ratio based on diagonal?

No. Divide lens-to-screen distance by image width, not the diagonal.

What about ultra short throw?

UST ratios sit well below 0.5. Enter the chart pair; this math still holds.

Does lens shift change throw?

Shift does not change throw ratio much, but it can push you off the charted zoom window. Check the PDF.

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