Inch ruler
An actual-size ruler in inches.
This page opens the ruler in inches, with whole inches numbered and every line down to 1/16 of an inch. Like the main online ruler, it calibrates to your screen first, so one inch on the scale is one real inch on your phone, tablet, laptop or monitor.
Reading fractions of an inch
Each inch is split in half, then in quarters, eighths and sixteenths, and every split uses a shorter line than the one before. The longest line between two numbers is 1/2 inch. To read a measurement, take the last numbered inch and count the short lines past it: each one is 1/16 inch, two make 1/8, four make 1/4. A pencil that ends four sixteenths past the 5 is 5 1/4 inches long.
A full 12 inch ruler
A foot-long ruler needs a screen at least 12 inches wide. Most 15-inch and larger laptops and every desktop monitor have that, so press F for fullscreen and the whole scale fits across. On a phone or small tablet, drag a guide line out of the ruler to mark where the screen ends, move the object along and add the two readings.
Check the calibration with a card
A bank card is 3 3/8 inches long and 2 1/8 inches tall, and the ruler shows a blue mark at both lengths. Hold a card against the ruler with its corner at 0. If its edge lands on the mark, every inch on the screen is correct. If not, open Calibrate and use the Credit Card method, which is typically accurate to about 1/16 inch over 6 inches.
Prefer metric?
Switch to the centimeter ruler, or press 1 on this page. The chart below converts whole inches to centimeters and millimeters, and the fraction chart on the home page converts 1/16-inch steps to decimals.
Inches to centimeters and millimeters
| Inches | Centimeters | Millimeters |
|---|---|---|
| 1 in | 2.54 cm | 25.4 mm |
| 2 in | 5.08 cm | 50.8 mm |
| 3 in | 7.62 cm | 76.2 mm |
| 4 in | 10.16 cm | 101.6 mm |
| 5 in | 12.70 cm | 127.0 mm |
| 6 in | 15.24 cm | 152.4 mm |
| 7 in | 17.78 cm | 177.8 mm |
| 8 in | 20.32 cm | 203.2 mm |
| 9 in | 22.86 cm | 228.6 mm |
| 10 in | 25.40 cm | 254.0 mm |
| 11 in | 27.94 cm | 279.4 mm |
| 12 in | 30.48 cm | 304.8 mm |
FAQ
Questions, answered.
Is this inch ruler actual size?
Yes, once it’s calibrated to your screen. Auto-Detect recognizes most phones, tablets and Macs; on other screens, enter your screen diagonal or match a credit card. Check it by holding a card at 0: its long side should end at 3 3/8 inches, on the blue card mark.
How do I get a 12 inch ruler on my screen?
Press F for fullscreen. Most laptop and desktop screens are wider than 12 inches, so the full foot fits across the top edge. A 13-inch laptop is about 11 inches wide, so on smaller screens measure in two parts: mark 6 inches with a guide line, slide the object and add the readings.
What are the small lines on an inch ruler?
Between two numbered inches, the longest line is 1/2 inch, the next shorter lines are 1/4 and 3/4, then eighths, and the shortest lines are sixteenths. Count sixteenths past the last whole inch: 3 inches plus 5 short lines is 3 5/16 inches.
How many centimeters are in an inch?
Exactly 2.54 centimeters, or 25.4 millimeters. The inch has been defined that way since 1959, so 12 inches is 30.48 cm.
Can I measure inches on my phone?
Yes. Open this page on your phone, check the status shows your phone model (or calibrate with a credit card), then lay the object on the screen at 0. Turn the phone to landscape for about 5 to 6 inches of ruler on most phones.
What can I use as a 1 inch reference?
A US quarter is 0.955 inches across, just under an inch. A credit card is 3.370 × 2.125 inches, and US Letter paper is 8.5 × 11 inches. Any of these lets you check the ruler at a glance.
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