Inch Ruler Online (Actual Size)
An on-screen ruler in inches with 1/16″ marks. The readout gives the length as a fraction (like 3 ⅝″) and as a decimal.
How to measure in inches
- Set zoom to 100%. Press Ctrl + 0 (⌘ + 0 on Mac). After calibrating, the ruler corrects itself automatically if you zoom.
- Press Calibrate. Hold a credit card, debit card, ID or gift card flat against the screen and resize the on-screen card until it matches. No card? Use a coin, a dollar bill, a sheet of A4 or Letter paper, your screen size, or pick your device from the list.
- Save. Your calibration is stored on this device only, so next time the ruler opens at true size.
Then place the object at 0 and tap where it ends. Use the ↕ button to rotate the ruler on a phone for more length.
Inch fractions chart
Use this chart to convert ruler marks to decimals and millimeters:
| Fraction | Decimal inch | Millimeters |
|---|---|---|
| 1/16″ | 0.0625 | 1.59 mm |
| 1/8″ | 0.1250 | 3.17 mm |
| 3/16″ | 0.1875 | 4.76 mm |
| 1/4″ | 0.2500 | 6.35 mm |
| 5/16″ | 0.3125 | 7.94 mm |
| 3/8″ | 0.3750 | 9.52 mm |
| 7/16″ | 0.4375 | 11.11 mm |
| 1/2″ | 0.5000 | 12.70 mm |
| 9/16″ | 0.5625 | 14.29 mm |
| 5/8″ | 0.6250 | 15.88 mm |
| 11/16″ | 0.6875 | 17.46 mm |
| 3/4″ | 0.7500 | 19.05 mm |
| 13/16″ | 0.8125 | 20.64 mm |
| 7/8″ | 0.8750 | 22.22 mm |
| 15/16″ | 0.9375 | 23.81 mm |
| 1″ | 1.0000 | 25.40 mm |
Common things measured in inches
- Screen sizes (measured diagonally)
- Photo prints: 4×6, 5×7, 8×10 inches
- Screws and bolts: #8, ¼″, 5/16″ and more
- Paper: US Letter is 8.5 × 11 inches
- Waist and inseam measurements; use the printable tape measure
Need a paper ruler?
Print a 12 inch printable ruler with 1/16″, 1/8″ or decimal 1/10″ marks.
FAQ
How big is 1 inch on my screen?
Calibrate the ruler, then the distance from 0 to 1 on the inch scale is exactly one inch. Without calibration, browsers assume 96 pixels per inch, which is rarely right on phones and laptops.
How many centimeters are in an inch?
Exactly 2.54 cm, or 25.4 mm.
How do I measure inches on my phone?
Open this page on your phone, press Calibrate and match a credit card or coin, then switch to the vertical ruler. Most phones show about 5 to 6 inches vertically.
What are the small lines on an inch ruler?
They split each inch into 16 parts. From longest to shortest: 1/2, 1/4, 1/8 and 1/16 of an inch.
More tools
Printable ruler
Make a custom paper ruler: inches (1/16, 1/8 or tenths), cm/mm, 6 in to 1 m, Letter or A4.
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