The room supplies one lens-to-screen distance of 3 metres. The projector range is 1.2–1.5 and the planned image is 16:9. Because distance is fixed, the larger throw ratio produces the smaller image width.
Invert the endpoints in the correct order
Minimum width is 3 ÷ 1.5 = 2 metres. Maximum width is 3 ÷ 1.2 = 2.5 metres. Keeping the original ratio order for the widths would reverse the physical range, so ThrowFit explicitly uses the maximum ratio for the minimum size.
Convert the width range to diagonal
For 16:9, diagonal = width × √337 ÷ 16. Widths of 2–2.5 metres therefore correspond to approximately 90.34–112.93 inches diagonal, with heights of about 1.13–1.41 metres. The displayed endpoints are rounded only after exact unit conversion.
Three metres must mean the optical distance
If 3 metres describes wall-to-wall room depth, subtracting projector body, rear cables, mount offset, screen stand-off, and installation clearance may leave a shorter lens distance. Measure the actual reference points before treating the inverse result as available screen size.
Use the result to shortlist, not certify
The 90–113 inch interval can eliminate clearly incompatible screen plans or help compare lens ranges. Final size still depends on focus, brightness, image-size limits, surface, ambient light, and viewing requirements that this geometry tool deliberately does not predict.