Plan Print Scaling Calculator

What this calculator solves

This tool converts an approved source scale into a print-dialog or RIP percentage. It is useful when a 1:100 plan must be issued at 1:50, a large sheet must be reduced for a site set, or a scanned legacy drawing needs a controlled first correction.

The calculation does not select media or bypass verification. Enlarging a sheet may exceed the PDF page box or device width, so calculate the target footprint with the Plot Sheet Fit Planner before releasing output.

How to choose the inputs

Read the source denominator from the approved file only after checking a known dimension. Enter the required issue scale as the target denominator. Both inputs are unitless ratio numbers; 1:50 and 1:100 can be compared without adding millimetres or inches.

Select the target ratio from the project drawing list or recipient requirement, not from whichever paper happens to be loaded.

How the calculation works

Print percentage = source denominator ÷ target denominator × 100. Changing 1:100 to 1:50 therefore requires 100 ÷ 50 × 100 = 200%. Changing 1:50 to 1:100 requires 50%.

Values over 100% enlarge; values below 100% reduce. Enter the calculated value as a custom scale and disable “Fit,” “Shrink oversized pages” and other automatic page-sizing options when exact scale is required.

Worked production example

A subcontractor receives an A3 detail marked 1:100 but needs a 1:25 shop set. The calculated output is 400%. A 100 mm source scale bar should therefore measure 400 mm after printing. That enlarged footprint will not remain on A3, so the operator must choose a larger roll or tile the plan.

Write the source ratio, target ratio, calculated percentage, driver setting and measured check length on the production ticket.

How to interpret the result

More than 100% makes the physical page larger and less than 100% makes it smaller. The percentage is a device instruction for this source-to-target pair, not proof that the viewer or driver applied it correctly.

Common production mistakes

The most frequent error is reversing the fraction: 1:100 to 1:50 is an enlargement, not a 50% reduction. Another is applying a custom scale on top of a PDF that was already exported or scanned at a different percentage.

Do not infer the source scale from sheet size alone. A drawing can carry a nominal scale while the page has been reduced for tender, email or record storage.

Related production workflow

Calculate the ratio change here, confirm the enlarged footprint against paper, set the custom RIP percentage and output one proof. Record the measured check dimension before releasing a full site or tender set.

Production assumptions and limitations

The result assumes equal horizontal and vertical scaling and a source file whose geometry matches its stated ratio. Printer calibration, page-box offsets and paper movement are outside the formula. Always verify a known dimension on the first physical output.

Continue with Printed Scale Verification and the exact-scale plotting checklist. Last reviewed: 2026-08-24.