Brick Builder: Free 3D Building Brick Simulator with Bridges and Strength Test

Free virtual brick builder in your browser: stack bricks, plates, slopes, arches and wheels in 3D, start from 20+ example builds for kids (house, car, rocket, castle) and engineering (beam, arch and cantilever bridges, crane, corbel arch), follow them step by step, put weights on your build and find its breaking load, then take the parts list or an STL file. No sign-up, nothing to install.

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Show stress colours fine working hard breaks Stuck to the baseplate Stud grip Weight tool puts g

Breaking test

Click a brick with the ⚖ Weight tool (or pick one below), then find out how much it can hold.

How is the strength worked out?

Every part's weight (and any weight you add) flows down through the parts under it to the baseplate. Two things can go wrong:

Overhang: when the weight carried by a part sits past the edge of what it rests on, the studs have to pull to stop it tipping. Each stud grips with about 1.5 newtons; more studs further from the edge hold more.
Bending: a part that spans a gap bends like a beam. Parts stacked on top over the gap bend with it, so a deck three plates thick is far stiffer than one plate. If it sags more than 1/40 of the span, the studs pop off.

Smooth tiles and the sloped faces have no studs, so nothing on them is held. It is a simple model for learning, not an engineering tool: real bricks also stretch, twist and wear out.

A free virtual brick builder for kids and grown-ups

MES Brick Builder is a 3D building-brick simulator that runs in your browser. Pick bricks, plates, slopes, arches and wheels, choose a colour and click to stack them on the baseplate. Start from one of the example builds, follow them step by step with your own bricks, or test how strong your bridge is. Nothing is uploaded and there is nothing to install.

How to build

Choose a part on the left (for example Brick 2x4) and a colour.
Click the baseplate: the brick drops onto whatever is under it. Click the top of a brick to stack, or its side to build next to it.
Press R (or ⟳ Turn) to turn the brick. Shift-click a brick to take it off, Ctrl+Z to undo.
Drag to look around, right-drag to move the view, scroll or pinch to zoom.

Bridges and engineering

Press 💥 Crash test to send your build, or a ready-made car, into a concrete wall, a brick wall or another car and watch which studs let go.

The Strength tab colours every part by how hard it is working. Put weights on your build with the ⚖ Weight tool and press Find the breaking load to see how much it can hold and which part gives up first. The engineering examples show why bridges have piers, why a thick deck beats a thin one, how arches and corbel arches work, why bricks are laid in a staggered pattern, and how a crane's counterweight stops it tipping. Then try the challenges: cross the river with a bridge that holds 1 kg, or reach out 10 studs from a wall.

Questions

Does it work with real bricks?: Yes: the sizes are the usual ones (a stud is 8 mm, a plate 3.2 mm, a brick three plates), so a build here can be made with LEGO®-compatible bricks you already have. The Parts list tab tells you what you need, and the Steps tab shows the order.
How do I share my build?: Press Share link and send it: the whole build is inside the link. Save makes a file you can open again on any computer.
Can I 3D print my build?: Press STL to download the whole build as one model for a 3D printer's slicer.
Is it the official LEGO app?: No. MES Brick Builder is an independent, free project and is not made, sponsored or endorsed by the LEGO Group. LEGO® is a trademark of the LEGO Group.

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