Printing one test page can save you from assembling a pattern at the wrong scale. The useful measurement is the dimension printed on the test shape, compared with the same dimension on your paper copy. Check the horizontal and vertical directions separately before printing the rest of the file.
Sewlore's printing and assembly instructions advise using 100% or Actual Size and turning off Fit to Page. Follow the instructions for your particular pattern: the test square and page selection may differ between files.
Use the reference shown in the file
Do not assume every pattern uses a 100 mm square. For example, Sewlore's free leaf applique bookmark file uses a 50 mm test square. Its public guide tells you which page to print and which additional rectangle dimensions to check.
Measure the reference in the same units as its label, or convert deliberately before entering it into a checker. Read the defined outside edges consistently. If the guide gives a specific measurement method, use that method.
Calculate the size difference
For each direction, calculate:
Scale difference = (printed length ÷ intended length − 1) × 100
The following values are hypothetical examples, not results from a Sewlore printer test.
Suppose a 100 mm reference prints as 97 mm wide and 97 mm tall. In each direction, 97 divided by 100 is 0.97. Subtract one and multiply by 100: the result is −3%. The page is 3% smaller than the intended scale along both axes.
That does not mean the pattern's size label is wrong. It means the printed page failed this scale check. Review the paper format and printing settings before printing more sheets.
A second example uses the same 100 mm reference, but the paper measurement is 98 mm wide and 100 mm tall. The horizontal difference is −2%; the vertical difference is 0%. One overall zoom adjustment cannot correct both directions at once. Recheck the measurement, PDF viewer, printer settings and output before proceeding.
Inspect the settings before compensating
Return to the original PDF and its instructions. Confirm that the selected page size matches the file, then inspect the print dialog for scaling controls. Reset an unintended Fit or Shrink setting, print just the reference page again and remeasure.
The Sewlore PDF Print Scale Checker makes the comparison from your inputs. Use its signed differences to describe the problem. A calculator cannot determine why a printer or viewer changed the size, and it cannot verify an unmeasured paper copy.
There is a mathematical ratio for compensating a uniform size error: intended length divided by printed length. For the 97 mm example, that ratio is about 1.0309. Treat this as an explanation of the arithmetic, not the first printing instruction. Restore the documented settings and verify a new test page first. An unequal horizontal and vertical result needs investigation rather than one global percentage.
Keep a brief print record
Write down the file name, paper format, viewer, print setting and measured width and height. That makes it easier to reproduce a successful setup and to explain a failed one when asking for help. Check that printed content has not been cut off at the edges as well as checking its scale.
Once the reference meets the pattern's instructions, use its page index and assembly marks for the full print. A correct reference measurement verifies print scale for that output; it does not establish garment fit or replace a fitting sample.
By Sewlore. The examples are illustrative. Read the printing guide and the instructions included with your individual PDF before cutting fabric.