Online RulerRead centimeters on screen
Select centimeters in AR Ruler. Set one edge of the object at zero and read the mark at the opposite edge. The numbered marks give whole centimeters, and the small divisions between them let you record the extra length as a decimal part of a centimeter.
- Read the last numbered mark before the far edge to find the whole-centimeter part.
- Count the millimeter spaces from that numbered mark to the far edge. Each space adds one tenth of a centimeter.
- The movable marker measures from zero, so keep the object’s starting edge on the zero tick when reading the marker directly.
- Open the centimeter scale on the screen you calibrated. If the display or browser zoom has changed, check the scale with your bank card before placing the object.
- Set the edge you want to measure beside the ruler so the marks remain visible. Align the starting end with zero and keep the edge parallel to the scale.
- Find the tick at the far end. Move the marker to that point if it helps you keep track of the reading when you lift the object.
- Read the whole centimeters, then count the small spaces beyond that mark. Write the combined reading in centimeters, using a decimal point when needed.
Count spaces from the number
Use the last whole-centimeter line as the place to begin counting. The gap from that line to the next small tick is the first millimeter space. Keep counting the gaps until you reach the object’s end. At the next numbered line, read that number as a whole centimeter. For an end that falls before the first numbered centimeter, write zero before the decimal point and use the spaces from zero for the decimal part.
Measure width or height
Decide which dimension you need before placing the object. For width, use the two edges that bound the width. To measure height with a horizontal ruler, turn the object until its height runs along the scale. Keep the same starting and ending edges in mind as you turn it. If the sides curve, use the points where the object reaches farthest in the direction you are measuring. Look straight at each end as you line it up.
Read a partly covered scale
If the object hides the ticks, slide it slightly to the side while keeping it parallel to the scale. Check zero again after the move. When you can see the ticks beside both ends, line up the marker with the far end and lift the object to read the mark. If you have to start at a numbered mark other than zero, subtract that starting value from the ending reading to get the length.
Should I write cm or mm?
Use cm when you record the numbered reading with a decimal part. If you need mm, count the small spaces across the full length and label the result mm.
What if the edge is between small ticks?
Record the nearest mark if an approximate reading is enough. If you need to show where the edge falls, write the two marked values that bound it.
Can I use the same card calibration for centimeters and inches?
Yes. Select the unit you want on the calibrated ruler. Verify the scale if you change the browser zoom or move to another display.