New Geometry Shapes: A Real Geometry Box in pairPaint

What is in the geometry box?

Open Shapes and you will find a new section called Instruments. It holds six tools, the same six that live in a school geometry box — except these never get lost at the bottom of a school bag:

• Ruler — a 15 cm ruler with real markings, for measuring and drawing straight lines.
• Protractor — a 180° protractor for measuring and drawing angles.
• Compass — set the opening, then drag the pencil tip to draw circles and arcs.
• Divider — pick up a distance and carry it somewhere else on the canvas.
• 30-60-90 set square — for 30°, 60° and 90° angles.
• 45-45-90 set square — for 45° and 90° angles.

I built them as real canvas items, not pictures of tools. You place them, move them, resize them and rotate them, then draw along their edges — the way you would with a physical geometry box, but with undo.

How to add an instrument

Open the Shapes menu, pick an instrument, and it drops onto your canvas at the middle of your view, already selected. Drag it wherever you need it. Corner handles resize it, and you can rotate it to any angle. When you are done, it stays put while you draw — and if it is in the way, drag it aside or delete it like any other item.

Because the instruments live on the canvas itself, they work with everything else in pairPaint: put a ruler on graph paper, a protractor over a student's triangle, or a compass on a blank A4 page. They also show up in the same room as everyone else when you draw together online, so a teacher's protractor is visible to the whole class.

The ruler: straight lines that are really straight

The ruler is the workhorse. Line it up, then draw along its edge and your line follows the edge — no wobble, no guessing. The markings are real centimeters, so a segment drawn against the ruler measures what it claims to measure. Hovering over it shows a readout, which is handy when you want to check a length before committing to a stroke.

For younger kids, the ruler is also the simplest introduction to measuring: place it next to a sticker or a shape and read off how long it is. For older students, it turns the canvas into a proper drawing board for scale drawings and geometry homework.

One more thing the ruler can do: Real-size mode. Select anything, tap the ⋯ button in the floating menu, and switch Real size on — 1 cm on the canvas becomes 1 cm on your screen. Because a browser cannot know your screen's true physical size, you calibrate once: hold a real ruler against the 10 cm bar in the panel and drag the slider until they match. The calibration is saved on that device, so the ruler then measures true size every time.

The protractor: angles without the squinting

Angles are where physical geometry boxes get fiddly — the protractor slides, the pencil slips, and the reading is always a guess. On the canvas, the protractor sits still. Put its center on the vertex of your angle and read the measurement off the 180° scale.

When you start a line from the protractor's center, pairPaint snaps the line's angle to the nearest 5°, so drawing a clean 40° or 135° angle takes one drag instead of three attempts. That snapping is what makes the protractor genuinely useful for teaching: the class sees the angle being built, step by step, at exactly the size you meant.

The compass: circles and arcs at any size

The compass works the way a real one does. A slider handle sets how wide the compass opens — that opening is your radius. Then drag the pencil-tip handle and the compass draws the arc. Open it wide for a big circle, close it down for a small one. Because the radius is set before you draw, you can draw two circles with exactly the same radius in two places, which is the heart of most compass-and-straightedge constructions.

If you have ever watched a student fight a slipping school compass, you know why the digital version earns its place: the center stays where you put it, and the arc comes out clean the first time.

The divider: carry a distance across the canvas

The divider is the tool most people forget — until they need it. Set its points to span a distance, then carry that exact distance to another part of the drawing. It is how you copy a segment length without measuring it, mark equal spacings along a line, or step off equal parts around a shape. A point handle adjusts the span, and the divider holds it while you move.

The set squares: instant right angles and triangles

The two set squares give you the angles students meet first: 30°, 45°, 60° and 90°. Their edges work like the ruler's — draw along them for a clean angled line — so building a right triangle is a matter of placing the square and tracing two edges. Combined with the protractor, they cover nearly every angle a school lesson needs.

Ideas for the classroom

The geometry box shines brightest as a teaching tool, because the whole class watches the construction happen live. A few lessons that work well:

• Meet the angles — draw an angle with the protractor, then ask students to name it: acute, right, obtuse. Snap the line to the nearest 5° and let them read the measurement.
• Circle parts — draw a circle with the compass, then use the ruler to add a radius and a diameter. Label the parts with the text tool.
• Triangle by construction — give the class three side lengths, and build the triangle together with the ruler and compass, step by step.
• Measure everything — place the ruler next to shapes and stickers and have students estimate, then measure. Estimation games work for every age.
• Homework on the canvas — students open a blank page, construct the assigned figure with the instruments, and export it as a PNG or PDF to hand in.

For extra practice on paper, you can pair a canvas lesson with printed geometry worksheets — free printable collections like the ones at freekidworksheets.com make a good follow-up after the class has built the same figures on screen.

I keep more classroom ideas in 5 ways teachers use pairPaint in the classroom.

Why a geometry box belongs in a paint app

A paint app is where kids already draw, and a geometry lesson is drawing with rules. Putting the instruments where the drawing happens means no switching apps, no printing a worksheet just to measure something, and no lesson lost to "I forgot my geometry box." It also makes pairPaint a stronger free online whiteboard for math: the same canvas that hosts a class mural in the morning can host a geometry lesson in the afternoon.

That is the idea behind every tool I add: the best app for teacher and student drawing is the one that is already open. The geometry box is free, like everything else in pairPaint — open Shapes, pick an instrument, and start measuring.

Frequently asked questions