Projector brightness throw calculator

Find throw distance from image width × throw ratio, and ideal illuminance from lumens ÷ image area.

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Image width

Projector throw ratio

More inputs and assumptions

Image height

Light reaching screen (lumens)

Answer

…

Find throw distance from image width × throw ratio, and ideal illuminance from lumens ÷ image area.

More results

Precision and calculation record

Decimal places in numeric results and text downloads

Rounding changes displayed numbers, not the calculation. Text, fractions, matrices and CSV schedules keep their own formatting. Automatic keeps up to 12 significant digits, with money shown to cents where applicable.

Step-by-step calculation

Inputs are substituted below. Each line evaluates the next operation; intermediate values are displayed to 12 significant digits while the calculation uses full precision.

Saved scenario

Save the current answer, then change an input to compare. This clears when you leave.

Formula and assumptions

Use matching length units. Illuminance is lux only when dimensions are metres. Input light reaching the screen, not an assumed rated output. Lens offset, zoom limits, ambient light, gain and nonuniformity need separate specifications.

Automatic precision shows numbers to 12 significant digits. Thousands separators such as 1,000 are accepted; use a dot for decimals.

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Updated 2026-09-26

Using Projector brightness throw calculator

Find throw distance from image width × throw ratio, and ideal illuminance from lumens ÷ image area.

Next: Display size calculator

A worked example

Example inputs: image width = 2, projector throw ratio = 1.5, image height = 1.125, light reaching screen (lumens) = 1000. Lens-to-screen distance = 3.

Before you use the result

Example results for image width

These examples use Projector throw ratio: 1.5; Image height: 1.125; Light reaching screen (lumens): 1000. They are reference calculations, not recommended settings.

Image width	Lens-to-screen distance
1	1.5
2	3
4	6

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ToolOctopus. “Projector brightness throw calculator.” Updated 2026-09-26. https://tooloctopus.com/projector-brightness-throw-calculator.

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