Online Ruler Tool

About the Online Ruler

Have you ever needed to measure a small object, such as a ring or a bolt, and couldn't find a ruler? So did we; that’s why we decided to make a tool to fix that problem. Our online ruler is a free way for users to make sure they always have a ruler when they need one. Whether you are on a desktop, mobile phone, or tablet, this tool gives users an instant 1:1 scale ruler.

Likewise, for ease of use, we also added the choice to use inches, centimeters, or millimeters, and a measurement guide. To use the guide, you can click and drag the red circle on the ruler. This circle shows the measurement for the line above it. Using this guide, you can drag the line to the end of your item and easily get an exact measurement without needing to count.

Is the online ruler accurate?

The ruler becomes a 1 to 1 scale accuracy if it is properly calibrated. If this is the first time you opened the ruler on your device, you need to calibrate before use. After, your calibration will be saved.

With the screen size calibration, the ruler calculates the device's pixels per inch (ppi). So the tool knows your device's exact pixel size, and the manufacturer knows the exact screen size. From this info, we can calculate an accurate ppi. For example, an iphone 16 has a diagonal screen size of 6.1 inches and a resolution of 2556 by 1179 pixels. This converts to 460 ppi. So there are exactly 460 pixels in a single inch for the device. Using this data, we can then have a 1 to 1 scale ruler for your device.

The second method is to use a standard card size. So all debit and credit cards have a universal size of 3.37 inch width and 2.125 inch height. This is done so that all credit cards work in any country, and manufacturers follow this to a strict standard. By using this information, you can then use that standard size, and adjust the ruler to match it. Because the cards are very precise, the ruler is also precise.

Thus following these two standards, we are able to ensure that once calibrated, our ruler is accurate and to scale for every device. For more info on how to calibrate, read the question below.

How to Use and Calibrate

The largest issue with using an online ruler is the scale. To fix this issue, we provide two methods to calibrate the ruler. It is important to calibrate the ruler before you use it. You only need to calibrate the ruler once, as the settings are saved to your local browser. Then, every time you return to the tool, your ruler will be automatically calibrated.

The first method to calibrate the ruler is by looking up your device's screen size. Most phones or monitors will include the size of the device screen in inches within their specs. If you know this information, you can use the slider to adjust it to match your device's screen size. Then, the ruler will be accurately calibrated.

The second method is to use a standard-sized card. For example, across the world, credit cards, debit cards, and gift cards are standardized so they can work in any country. This size is a 3.37-inch width and a 2.125-inch height. By using this universal standard, we can calibrate the ruler. All you would need to do is use the slider on the top and adjust the ruler until the card width matches the dotted line width. Once the distance from the dotted line to the start of the ruler is the same width as the standard card, your ruler is calibrated. Because all card makers follow strict size guides, this makes for an accurate ruler as well.

Practical Applications

Almost everyone, at some point, has needed to use a ruler, so our focus was to make that as convenient as possible. One benefit is that we offer a slider so that you do not need to try to count the small lines on a ruler to see the measurement. All you need to do is move the slider to match the width, and you get a perfect measurement instantly.

Furthermore, most people already carry their phones wherever they go, so if you need a ruler in a hurry, you can just open the website. This is perfect for when you are traveling or at the store. In addition, you only need to calibrate the ruler once; even if you do not have a credit card, you can just open the website on the same device and the calibration will be saved.

Lastly, even if you do not have a credit or debit card, we also make sure to have a backup. Users can instead enter their device's screen size to calibrate the ruler. This is super simple and easy. All manufacturers post the exact device screen size, so all you need to do is look up your device’s screen size and adjust the ruler.