Origami Paper Size Calculator

About Origami Paper Size Calculator

The Origami Paper Size Calculator tells you exactly what size square to cut so your finished origami model comes out the size you want. Because origami is pure geometry, every finished dimension — a crane's wingspan, a masu box's side, a lily's height — is a fixed fraction of the paper's side length. Enter the finished size you are aiming for, pick a classic model (or calibrate with a quick test fold), and the calculator returns the required paper square, the closest standard kami sheets, and how the model would come out on every common paper size.

How to Use This Calculator

1. By model: choose a preset such as the traditional crane, masu box, water bomb, lily, jumping frog, butterfly, heart, or samurai helmet. Each preset carries a typical model-to-paper ratio; the masu box ratio is exact geometry (side = paper × √2⁄4 ≈ 0.354).
2. From a test fold: the most accurate method for any design. Fold the model once from any square, measure the dimension you care about, and enter the test paper size and the measured result — the calculator derives your personal ratio and scales it exactly.
3. Enter the desired finished size in cm, mm, or inches and click Calculate Paper Size.
4. Read off the square to cut, the closest standard sheet with its deviation, and tips for cutting the square from A4, US Letter, or A3 paper.

The Math Behind It

Origami scales linearly: doubling the paper doubles every dimension of the model. If a model's characteristic dimension is \( k \) times the paper side \( s \), then:

\[ s = \frac{\text{desired finished size}}{k} \]

For a test fold, the ratio is measured directly: \( k = \dfrac{\text{test result}}{\text{test paper side}} \). This single division is why one quick test fold lets you scale any model — even a complex design with no published dimensions — to an exact target size.

Typical Model-to-Paper Ratios

• 🕊 Traditional crane: wingspan ≈ 0.45 × paper side
• 📦 Masu box: side = 0.354 × paper side (exact), height = 0.177 × paper side
• 🎈 Water bomb: cube edge ≈ 0.35 × paper side
• 🌸 Lily / iris: flower height ≈ 0.50 × paper side
• 🐸 Jumping frog: body length ≈ 0.33 × paper side
• 🦋 Butterfly: wingspan ≈ 0.50 × paper side
• 💗 Simple heart: width ≈ 0.55 × paper side
• ⛑ Samurai helmet: width ≈ 0.70 × paper side

Approximate ratios drift a few percent with paper thickness and folding accuracy — every crease consumes a little paper, so heavy paper folds up slightly smaller. When the finished size really matters (gift boxes that must fit, modular units, jewelry-scale folds), calibrate with the test-fold mode using the same paper you plan to fold with.

Standard Origami Paper Sizes

Kami (standard origami paper) is sold in squares of 5 cm, 7.5 cm, 9 cm, 15 cm (6 in — the most common size worldwide), 17.5 cm, 20 cm, 24 cm and 35 cm, plus 3 in and 10 in packs in inch-based markets. If no standard square is close enough, you can cut your own: an A4 sheet yields a 21 cm square, US Letter an 8.5 in square, and A3 a 29.7 cm square — fold one corner to the opposite edge and trim the strip.

Frequently Asked Questions

How do I know what paper size to use for origami?

Divide the finished size you want by the model-to-paper ratio. A crane's wingspan is about 0.45 of the paper side, so a 10 cm wingspan needs roughly a 22 cm square. This calculator does the division and matches the answer to real sheets you can buy or cut.

What is the most accurate way to size paper for any model?

A test fold. Fold once from any square, measure, and let the calculator scale linearly. It is exact for that model, that paper, and your folding style — no published ratio needed.

Does paper thickness change the finished size?

Slightly. Each fold loses a little length in the crease, so thick paper and many-layer models (like the crane) come out a few percent smaller than pure geometry predicts. The effect is biggest on small squares.

Can I use rectangular paper?

Most classic models start from a square. Cut a square from a rectangle by folding one short edge onto the long edge at 45° and trimming the leftover strip; the calculator tells you whether A4, Letter, or A3 is big enough for your required square.

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