Unit block sizes - the standard chart and how to specify a classroom set
The standard unit block is about 5 1/2 x 2 3/4 x 1 3/8 inches, and every other shape is a multiple or half-multiple of that unit. This page gives the full chart in inches and centimeters, the piece mix of a 101-piece class set, and the tolerance language to put in an RFQ.
Size chart in inches and centimeters
Dimensions follow the classroom unit block system used by US suppliers. Confirm the tolerance if you are matching existing stock from another source.
| Shape | Length | Width | Thickness | Metric (cm) |
|---|---|---|---|---|
| Half unit | 2 3/4 in | 2 3/4 in | 1 3/8 in | 7.0 x 7.0 x 3.5 |
| Unit | 5 1/2 in | 2 3/4 in | 1 3/8 in | 14.0 x 7.0 x 3.5 |
| Double unit | 11 in | 2 3/4 in | 1 3/8 in | 28.0 x 7.0 x 3.5 |
| Quadruple unit | 22 in | 2 3/4 in | 1 3/8 in | 56.0 x 7.0 x 3.5 |
| Pillar | 5 1/2 in | 1 3/8 in | 1 3/8 in | 14.0 x 3.5 x 3.5 |
| Half pillar | 2 3/4 in | 1 3/8 in | 1 3/8 in | 7.0 x 3.5 x 3.5 |
| Ramp | 5 1/2 in | 2 3/4 in | 1 3/8 in | 14.0 x 7.0 x 3.5 (sloped) |
| Large triangle | 5 1/2 in | 2 3/4 in | 1 3/8 in | 14.0 x 7.0 x 3.5 |
| Small triangle | 2 3/4 in | 2 3/4 in | 1 3/8 in | 7.0 x 7.0 x 3.5 |
| Arch | 11 in | 2 3/4 in | 1 3/8 in | 28.0 x 7.0 x 3.5 |
Piece mix for a class set
| Shape | Pieces in 101-pc set | Why this share |
|---|---|---|
| Unit | 32 | The basic building block |
| Double unit | 20 | Walls and spans |
| Half unit | 18 | Fills gaps and teaches halves |
| Quadruple unit | 8 | Long spans and floors |
| Pillar and half pillar | 8 | Height and columns |
| Ramp and arch | 5 | Bridges and slopes |
| Triangle | 6 | Roofs and angles |
| Cylinder and other | 4 | Variety and grip |
How to specify a set
- Species and moisture content: kiln-dried hardwood, stated on the quotation.
- Finish: water-based, named in the tested configuration.
- Edges: rounded and sanded; no sharp corners.
- Tolerance: each shape a true multiple of the unit; check a sample set before bulk.
- Storage: a cart or shelf matched to the shape list.
Mixing sets from different suppliers
- Measure a unit and a double from each set; a 1-2 mm difference breaks stability.
- Match the shape list, not just the piece count.
- Keep one supplier per block corner where possible.
- Label the set with the supplier and model so top-ups match.
Questions buyers ask
- What is the standard unit block size?
- About 5 1/2 x 2 3/4 x 1 3/8 inches (14 x 7 x 3.5 cm). Half, double, quadruple and special shapes are multiples of the unit.
- Does the thickness matter?
- Yes. The 1 3/8 inch thickness is what makes pillars, ramps and arches stack with the unit. A thinner block changes the system.
- Can you match an existing set?
- Yes, if you send the unit length, width and thickness. We confirm the tolerance before the order so mixed sets stay stable.
Need a classroom quotation?
Send the room count, the categories and the destination market. We reply with MOQ, lead time and the report status for each model.