Online ruler v0.1.0

A ruler to drag and turn on the board, with inches or centimeters, and a line to measure. Or print a ruler at true size.

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How to use it

Pick inches or centimeters. Drag the ruler and turn it by the dot at its end.
Move the ends of the red line to make something to measure, and line the ruler up with its left end at 0.
Read it out loud. Tick “Show the length” to check.
For a ruler to hold, open “Print a ruler”. Print at 100% and check the 4-inch and 10-centimeter lines against a real ruler.

Measure the same line in inches and centimeters and ask which number is bigger and why.
Start the line at 1 instead of 0 and ask what the number at the other end means.
Estimate first: hold up your fingers for how many inches, then check with the ruler.
Print the ruler on card, cut it out and measure things around the room.
Round to the nearest half inch, then the nearest quarter, then the nearest sixteenth.

Is the on-screen ruler real size?

No. A projector or tablet is not a fixed size, so the marks are in proportion but not an exact inch. Use the printable ruler when real size matters.

Why is my printed ruler the wrong size?

The printer dialog is set to Fit to page. Choose 100%, Actual size or No scaling and measure the 4-inch and 10-centimeter check lines.

How fine are the marks?

Inches go to sixteenths, centimeters to millimeters.

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