Origami Paper Size Calculator
Calculate the square of paper an origami model needs from the finished size you want, using folding ratios for four complexity tiers, and the nearest kami size.
How origami paper size relates to finished model size
In origami, the finished model is always smaller than the starting sheet. The ratio between paper size and model size depends on the complexity of the design. Simple models use more of the paper’s area, while complex models with many layers fold the paper down to a smaller fraction of its original size.
The paper-to-model ratio formula:
Required paper size = Desired model size × Folding ratio
The folding ratio depends on model complexity:
| Complexity | Folding Ratio | Examples |
|---|---|---|
| Simple (few folds) | 2.5 - 3× | Boat, cup, hat |
| Moderate (20-30 folds) | 3 - 4× | Crane, frog, lily |
| Complex (40-60 folds) | 4 - 6× | Dragon, unicorn, modular units |
| Super complex (60+ folds) | 6 - 10× | Insects, detailed animals |
Standard origami paper (kami) sizes:
| Size | Dimensions | Best For |
|---|---|---|
| 7.5 cm | 7.5 × 7.5 cm (3") | Tiny models, earrings, decorations |
| 15 cm | 15 × 15 cm (6") | Most standard models, the most common size |
| 20 cm | 20 × 20 cm (8") | Moderately complex models |
| 24 cm | 24 × 24 cm (9.5") | Complex models |
| 35 cm | 35 × 35 cm (14") | Super complex, display pieces |
| 50 cm | 50 × 50 cm (20") | Large display work, usually cut from a roll |
Worked example, folding a crane:
You want a finished crane about 8 cm tall. Cranes are moderate complexity with a folding ratio of about 3.5×.
Paper needed = 8 cm × 3.5 = 28 cm
The nearest standard size above 28 cm is 35 cm. So use a 35 cm sheet, or cut a custom 28 cm square from larger paper.
Paper weight matters too. Standard kami is 60-70 gsm. For complex models with many layers, thinner paper (40-50 gsm, such as tissue foil) folds more crisply. For simple models, thicker paper (80-100 gsm) holds shape better.
Rectangle paper: Some traditional models (like the masu box) use rectangular paper. A4 paper (210 × 297 mm) has a 1:√2 ratio and works for many rectangle-based designs. US Letter (216 × 279 mm) is close to 1:1.29. This calculator sizes squares, which is what the overwhelming majority of models start from. For a rectangle, size the short edge with the ratio above and cut the long edge to whatever the diagram asks for.
A warning about the ratios. They are rules of thumb gathered from folding, not constants. Two designers can publish the same crane at ratios half a size apart depending on how much paper the base eats. Treat the number as a starting point and cut a test sheet before you commit good paper to a 60-fold model.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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