How accurate is the on-screen ruler?

Accuracy depends on the calibration data for your specific screen model. Carbide uses the known pixel density of your device to calculate real-world distances, which is typically accurate to within a millimetre or two for most modern phones. For critical measurements, cross-check with a physical ruler.

Does it work on any screen size?

Yes — phones and tablets alike. Larger tablets give you more ruler length to work with, which is handy for measuring longer objects.

Can I measure something longer than the screen?

The maximum measurable length is limited to the physical length of your screen. For objects longer than your screen, measure in segments and add the values.

Does the ruler work without internet?

Completely. The ruler is fully offline — it uses only the known specifications of your device's display to calculate measurements.

Ruler

APP

Measure small objects against a screen-calibrated ruler.

Best on the app

Ruler needs your phone's hardware

It calibrates to your exact screen size and uses touch precision. Download Carbide free to use it — plus all 111 tools, fully offline.

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What it does

Ruler turns your phone or tablet screen into a precise measuring tool for small objects. Place any item directly on the display and drag two handles to align with its edges — the length is calculated in real time in centimetres or inches. Carbide calibrates the ruler to your specific screen's pixel density so the graduation marks reflect real-world dimensions rather than just pixels. It's perfect for quick measurements when you don't have a physical ruler handy: checking a cable's diameter, confirming a part size before ordering, or measuring a photo print. Everything runs on your device — no internet connection, no sign-up, completely free and private.

How to use the Ruler

Open Ruler from the Measurement category.
Choose your preferred unit — centimetres or inches — using the toggle at the top.
Place the object you want to measure flat against the screen.
Drag the two coloured handles to align with the start and end of the object.
Read the measurement displayed in the result card above the ruler.

Frequently asked questions

How accurate is the on-screen ruler?: Accuracy depends on the calibration data for your specific screen model. Carbide uses the known pixel density of your device to calculate real-world distances, which is typically accurate to within a millimetre or two for most modern phones. For critical measurements, cross-check with a physical ruler.
Does it work on any screen size?: Yes — phones and tablets alike. Larger tablets give you more ruler length to work with, which is handy for measuring longer objects.
Can I measure something longer than the screen?: The maximum measurable length is limited to the physical length of your screen. For objects longer than your screen, measure in segments and add the values.
Does the ruler work without internet?: Completely. The ruler is fully offline — it uses only the known specifications of your device's display to calculate measurements.

Take Carbide everywhere

All 111 tools, offline, on iOS & Android — free.