Check the Print Scale First
Measure the line below with a physical metric ruler. It must be exactly 50 mm from end mark to end mark. If it is longer or shorter, correct the browser or printer scaling and print again.
Compare a Ring with the Circles
Choose a round ring that fits the same finger. Place it over the circles. The black line should sit just inside the ring opening with no background gap and no line hidden under the metal. If the opening falls between circles, record both sizes and confirm with a jeweller.
16.5 mm
17.3 mm
18.1 mm
18.9 mm
19.8 mm
20.6 mm
21.4 mm
22.2 mm
23.0 mm
23.8 mm
Print, compare, and verify the result
Browser Print Settings
Open the print dialog, select the correct paper, and choose 100% or Actual Size. Margins may remain at the printer default because the measurement elements sit away from the page edge. Print one page, measure the scale line, and continue only when it passes.
Why the Scale Check Controls Accuracy
Browsers and printer drivers may shrink a page to fit margins. A five-percent reduction turns a 20.0 mm circle into 19.0 mm, enough to change the suggested size by more than one US step. The ruler check detects the combined scaling applied by the browser, PDF viewer, driver, and printer.
How to Align an Existing Ring
Look straight down and centre the ring over a circle. Compare the inner edge rather than the outside wall. A shadow can make the opening appear smaller, so use bright, even light. Rotate the ring and compare again; unequal readings suggest the ring is not perfectly round.
Why This Page Does Not Promise a Perfect Fit
The circles measure a ring opening after successful printing. They do not account for finger swelling, knuckle shape, band width, or a different interior profile. A ring that fits one hand may not fit the matching finger on the other. Use the result as a cross-check.
When to Use a Finger Gauge Instead
Visit a jeweller when no suitable ring is available, the finger base and knuckle differ substantially, the proposed band is wide, or the ring is costly or difficult to resize. A rigid gauge can be matched to the finished width and tested over the joint.
Save as PDF
The browser print dialog can save this page as a PDF. Reopen that PDF and print it at Actual Size, then repeat the 50 mm ruler check. Saving does not preserve physical scale unless the later print step also avoids page fitting.
Test the Ruler, Not the Page Border
Paper margins and browser headers can move content without changing its scale. The 50 mm line is the calibration target. Measure between its vertical end marks with a trustworthy ruler. If it reads 49 or 51 mm, the circles are not valid even if the page looks centred and the printer reports 100%.
Paper and Printer Limitations
Moisture, printer feed, and paper type can introduce small dimensional changes. Use ordinary stable paper, allow ink to dry, and avoid a curled sheet. Home printing is suitable for an estimate when the scale passes; it does not certify the device or replace a professional ring gauge.
Comparing Between Two Circles
If the inner wall exposes one circle but covers the next, the ring sits between those printed references. Do not squeeze the ring or choose whichever label you expected. Record both circle sizes and measure the opening with a calliper if available. The calculator can compare the decimal reading.
Printing from a Saved PDF
Saving through the browser creates a convenient local copy, but the later PDF viewer may apply its own Fit or Shrink option. Select Actual Size again and remeasure the scale line on every new printer. A previously successful file does not guarantee that another device preserves the same physical output.
Dispose of a Damaged Sizer
Creases, tears, moisture, and repeated handling can change a paper tool. Print a fresh sheet when the circle edge is damaged or the scale line no longer lies flat. Keep the recorded physical dimension with the nominal size so a jeweller can verify it independently.
Circle Accuracy Check
After the scale line passes, place a calliper across one printed circle if available. The US 10 circle should be about 19.8 mm across its inside line. This second check can expose a reading mistake or print distortion. If either check fails, do not compensate mentally; correct the print settings and produce a fresh sheet.
Using the Sheet Away from Home
Write the printer, date, and successful 50 mm check on the sheet before taking it to another location. Keep it flat in a folder. If it bends or becomes damp, print again. The physical page is the measurement reference, while a photo or screenshot of it has no reliable scale.
After You Choose a Circle
Record the nominal size and printed diameter, then compare that value with the seller's chart. If the seller lists a different diameter for the same label, ask which measurement governs its product. For an expensive ring, bring the reference ring and printed result to a jeweller for a mandrel and finger-gauge check.
Final verification step
Use black ink or a high-contrast setting so the circle boundaries remain crisp. Draft or economy mode is acceptable only if the lines stay complete and the scale still passes. A blurred or broken edge makes alignment subjective, so reprint before comparing a valuable reference ring.
Label the printed result
Record the selected US size and its printed millimetre diameter. If a seller assigns another label to that diameter, ask which measurement governs its product. Keep the sheet flat until the order is confirmed.
Sources and methodology
Dimensions are derived from inside circumference and rounded consistently. International labels are practical equivalents because national scales do not share every increment.