Ruler the actual size

Mobile version here

Your browser does not support the canvas element.

Graduation of an inch: ",, Pixels per inch :, Screen resolution:

Handy & Accurate Online Ruler

This is a convenient online ruler that could be calibrated to actual size, measurements in cm, mm and inch, the upper half is the millimeter ruler and centimeter ruler, the lower half is an inch ruler. In order to accurately measure the length of your item, we strongly recommend that you calibrate this online ruler first, set the correct pixels per inch to your own device, after adjustment, you will have the most precise ruler online.

How to adjusting this virtual ruler to actual size

To have the most accurate ruler online, just set the pixels per inch(PPI), below are some ways to know the pixels per inch to your device.
  1. My laptop has a wide screen (13.6"x7.6"), and resolution is 1366x768 pixels, 1366 / 13.6 = 100.44 PPI. The screen resolution of your current device is 1366x768 pixels.
  2. Search "display by pixel density" online, check if there has your device's brand and model, i am lucky and found my screen has 100 PPI.
  3. Use standard objects to compare lengths, check your wallet, use any paper money to be our compare object, then search "the width of your paper money" online, when you know the width, you can adjust the ruler's PPI setting by it, you can compare to any standard size object at your side, e.g., coin, credit card, CD, paper money, mobile phone, in the office, a A4 size printable paper is a good comparison object, the longer the more accurate. Below ruler adjuster help us to calibrate accuracy more easily.
  4. The most accurate way, after i measure the size of virtual ruler by an actual ruler, i found the markings are not very accurate at 30cm, so i adjust the default pixels per inch(PPI) to 100.7, now i have the most accurate virtual ruler on the web.
  5. Each device has it's own PPI, eg. my Asus laptop is 100.7 PPI, Apple MacBook Air is 127.7 PPI, Xiaomi Mi Pad 3 is 163 PPI, my mobile phones (Sony Xperia C5, OPPO R11 Plus) are both 122.6 PPI, Apple iPhone 5 is 163 PPI, iPhone 7 is 162 PPI, iPhone X is 151.7 PPI.

Adjust the ruler on the screen by Setting pixels per inch according to your own device, then you can use the correct ruler.
Pixels per inch: , select an actual widget as the standard to align the ruler on the screen, then increase/decrease the number of pixels in the cell and press the Pixel Settings button to save: