Pocket Ruler cm
Calibrate before measuring.
Turn your phone sideways for a longer ruler.
Match a real object
Place the short edge of a standard bank card against the line below. Adjust until both ends match. With a physical ruler, select 15 cm for a longer, more accurate comparison.
The full reference does not fit. Use landscape and Full screen, or shorten the scale until both endpoints are visible. If 15 cm still cannot fit, select the 5 cm reference.
Saved only on this device. Recalibrate if display scaling changes. Keep browser zoom at 100%. Check against a real ruler for precise work.
Correct scale · 10 cm reads 10.2 cm
With a physical ruler, measure the distance from this app’s 0 mark to its 10 cm mark. Enter that real distance below. Apply only once per comparison, then check again.
Your reported 10.2 cm span needs a 1.96% reduction.
Install & measurement tips
In Chrome, open the menu and choose Install app or Add to Home screen. After the first visit, the ruler works offline.
Align your object with the zero mark, not the edge of your phone. Each small division is 1 mm. Full screen tries to lock landscape; if unsupported, rotate your phone manually and enable auto-rotate.
Colours match your chosen phone palette: black, dark olive and pale yellow, in both light and dark mode.