Classroom ruler
Use a 0 to 30 centimetre or 0 to 300 millimetre ruler with clear tick marks.
Free maths tool
Length tool
A free classroom ruler for measuring a line, changing its length and switching between centimetres and millimetres.
Adjustable line
Drag the line handle or use buttons to change the measured length.
Two units
Switch between centimetres and millimetres while keeping the same measured line visible.
Live readout
Read the current length in the status panel and on the line label.
What the tool does
The length tool gives teachers and students a focused ruler model for discussing measured line lengths.
- measure a line on a visible ruler
- change the line length by dragging the handle
- increase or decrease the length with stepper buttons
- switch between centimetres and millimetres
- read the current length from the label and status panel
How teachers use it
Open it on a classroom display when students need to see how a line aligns with ruler ticks before answering measurement questions.
- set a length and ask students to read it from the ruler
- switch from centimetres to millimetres and discuss the same length in a smaller unit
- drag the handle slowly so students can track the changing endpoint
- ask students to predict the new length before using the plus or minus buttons
Why it is useful
Ruler reading depends on lining up an endpoint, attending to the scale and naming the unit. A large shared ruler makes those details visible.
- supports centimetre and millimetre vocabulary
- makes endpoint alignment and tick marks clear
- works as a model before independent measurement practice
Frequently Asked Questions
Is the length tool free?
Yes. Teachers, students and families can open the length tool in a browser for free.
Can it measure in centimetres and millimetres?
Yes. The tool can show the ruler in centimetres or millimetres while measuring the same line.
Can students change the line length?
Yes. Students can drag the handle or use the plus and minus buttons to change the measured line.
Is this different from the measurement practice app?
Yes. The length tool is an open ruler model, while the measurement practice app gives students practice questions.