A 6-inch ruler on your screen
A 6-inch ruler is the small ruler from a pencil case or a sewing kit. It's handy for hems, seam allowances, jewelry, small parts and photos. This page opens an inch ruler along the left edge of your screen, marked every 1/16 inch. Switch to centimeters at the top if you need them.
Related guides: How to Measure Without a Ruler
How to use it
- Tap Calibrate and match a bank card, or let the page detect your device.
- Hold the object against the left edge of the screen with one end at 0.
- Read the length to the nearest 1/16 inch. On a computer, hover over the ruler to see the exact fraction.
Good to know
- 6 inches = 15.24 cm = 152.4 mm, or half a foot.
- A 6-inch ruler has 96 sixteenth-inch marks.
- The long side of a 4×6 photo is exactly 6 inches; a US dollar bill is 6.14 inches long.
Does 6 inches fit on your phone screen?
Screen height in portrait, calculated from Apple's published resolution and pixel density (pixels ÷ PPI). The browser's bars use a little of it, so turn on fullscreen:
| Phone | Screen height | Fits 6 in? |
|---|---|---|
| iPhone 18 Pro Max, 17 Pro Max, 16 Pro Max | 6.23 in (15.8 cm) | Yes |
| iPhone Air | 5.95 in (15.1 cm) | Almost |
| iPhone 18 Pro, 17 Pro, 17, 16 Pro | 5.70 in (14.5 cm) | No |
| iPhone 16, 15 | 5.56 in (14.1 cm) | No |
| iPhone 17e, 16e | 5.50 in (14.0 cm) | No |
- Things close to 6 inches: the long side of a 4×6 photo (exactly 6 in) and a US dollar bill (6.14 in). A 3×5 index card is 1 inch shorter.
- For longer objects, use the 12-inch ruler or the online tape measure.
Three ways to calibrate
Auto-detect your device
The ruler recognizes about 130 phones, tablets, laptops and monitors, including iPhones, Galaxy phones, Pixels and MacBooks.
Enter your screen size
Enter your screen's diagonal size (for example, 15.6" for a laptop), and the ruler works out the scale from your screen resolution.
Calibrate with a bank card
Hold any bank card against the outline on screen and move the slider until they match. Bank cards are the same size everywhere: 85.60 × 53.98 mm.
How accurate is the ruler?
How accurate the ruler is depends on how well it knows your screen's pixel density, meaning how many pixels fit in an inch. There are three ways to set it, from most to least accurate:
Bank card (±0.5%): Bank and credit cards are made to one worldwide size, 85.60 × 53.98 mm (ISO/IEC 7810 ID-1). Because every card is exactly the same, matching one on screen gives the most accurate result.
Auto-detect (±1%): The ruler looks up your device's published screen size and resolution. Screens of the same model can differ very slightly, so this is a little less exact. It covers about 130 devices.
Screen size (±2%): You type in your screen size, and the ruler works out the rest from your resolution. Advertised sizes are rounded (a "15.6-inch" screen may really be 15.59 inches), so this is the least exact method. It's a good fallback when you don't have a card.
Real-life objects to check your measurements
Use these everyday objects to confirm the ruler is calibrated correctly.
Bank or credit card: 85.60 × 53.98 mm (3.37 × 2.13 in)
A4 paper: 210 × 297 mm (8.27 × 11.69 in)
US Letter paper: 8.5 × 11 in (215.9 × 279.4 mm)
US quarter: 24.26 mm (0.955 in) across
1 euro coin: 23.25 mm (0.915 in) across
AA battery: about 50.5 mm long and 14.5 mm wide