📚 7 measurement guides

Measurement Guides and Tutorials

Practical, no-fluff guides about measurement, calibration, unit conversion, and getting the most accurate results from a screen-based online ruler.

Sizing Guides 6 min read

How to Measure Your Ring Size at Home (Without a Sizer)

Three accurate methods to measure your ring size at home using string, a ruler, or an existing ring. Plus a free conversion chart.

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How-To Guides 5 min read

How to Measure Without a Ruler: 10 Everyday Items You Can Use

No ruler? No problem. Learn the exact dimensions of 10 everyday items so you can measure accurately using what is already in your pocket.

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Technical 7 min read

Screen DPI Explained: Why Your Monitor Lies About Inches

Why a 1-inch line on your screen is not really an inch. CSS pixels, PPI, and why every online ruler must be calibrated.

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Conversions 3 min read

How Many Millimeters in a Centimeter? (Quick Chart + Conversion)

A centimeter equals exactly 10 millimeters. Quick conversion chart and the math behind why.

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How-To Guides 6 min read

How to Read a Ruler in Inches and Centimeters (Complete Guide)

A complete guide to reading every tick mark on a ruler in inches, fractions, and centimeters, with the most common mistakes explained.

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Conversions 4 min read

Convert CM to Inches Without a Calculator (Fast Mental Math)

Three mental-math shortcuts to convert CM to inches without a calculator, plus the exact formula and a chart for common sizes.

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How-To Guides 5 min read

How to Measure Your Pupillary Distance (PD) at Home

Need your PD for online glasses orders? Three accurate methods to measure pupillary distance at home, including the mirror method that takes 30 seconds.

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Try Our Free Measurement Tools

Online Ruler (CM, MM and Inches) Free all-units online ruler with credit-card calibration
Online Ruler in Centimeters Measure in CM with 0.5 mm accuracy after calibration
Online Ruler in Inches Imperial inch ruler with 1/16 inch tick marks
Millimeter Ruler Online Precision MM ruler for ring sizing, screws, and jewelry
Actual Size Screen Ruler True 1:1 scale measurements on any calibrated device
Online Measuring Tape Scrollable virtual tape up to 50 cm or 20 inches
Credit Card Size Reference ISO 7810 ID-1 standard: 85.6 mm by 53.98 mm