ThrowFit
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Reviewed 16:9 example

How far back for a 100-inch projector screen?

A 100-inch 16:9 image is about 87.16 inches wide. Multiply that width by the projector’s actual ratio range.

Local geometry

Projector fit

No model lookup
Projected image aspect ratio
Known screen
Projector throw-ratio range
Use the same value for a fixed lens.

Measure from the lens reference point to the image surface. Body depth, cables, zoom limits, lens shift, offset, focus, brightness, keystone, mounts, and tolerances are outside this geometry.

Calculated geometry

Lens-distance range

Place the lens within≈ 2.66–3.32 m
Lens distance≈ 2.66–3.32 m8.72–10.89 ft
Image diagonal100 in254 cm
Image width≈ 87.16 in221.38 cm
Image height≈ 49.03 in124.53 cm
Throw ratio1.2–1.5

D = W × r = 87.16 × 1.2–1.5

The aspect-ratio diagonal usually introduces a square root. ThrowFit keeps exact decimal inputs and unit conversions, then marks rounded display values with ≈.

Verify the final range, reference point, focus limits, and mounting clearance in the current manual for the exact projector and lens.