ISO Paper Size Calculator
A, B, C series paper dimensions, nearest size, and weight per ISO 216
Size from Name
Find Nearest ISO Size
Calculate Weight
Common Sizes
ISO Paper Size
A3: 297 × 420 mm
Area
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Aspect Ratio
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Weight (80 gsm)
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ISO 216 Standard
An : 2-n/4 m²
Height / width = √2 ≈ 1.414 for all A series.
Each step halves the area: A(n) area = 2-n m² for A0.
A0 = 1 m² (841×1189 mm), B0 = 1.5 m² (1000×1414 mm), C0 = 1.297 m².
Weight: single sheet weight (g) = (area in m²) × gsm.
People Also Ask
📐 What are ISO A, B, C paper sizes?
A series for general printing (A0‑A10). B series for posters, envelopes (wider). C series for envelopes to fit A series.
📏 How are ISO paper sizes calculated?
Each size is half the area of the previous one, with sides in ratio 1:√2. A0 area = 1 m², B0 = 1.5 m², C0 = 1.297 m².
⚖️ How do I calculate paper weight?
Weight (g) = area (m²) × gsm. For A4 (0.0625 m²) at 80 gsm: 0.0625×80 = 5 g.
🌍 Which countries use ISO paper sizes?
Most of the world except US and Canada (Letter, Legal).
ISO Paper Size System
The ISO 216 standard defines the A, B, and C series of paper sizes. The base A0 has an area of 1 square meter. Each subsequent number (A1, A2…) has half the area of the previous size. The width and height are in the ratio 1:√2 ≈ 1:1.414, allowing easy scaling without cropping.
Series Differences
- A series – standard printing paper (A4 for documents).
- B series – intermediate sizes (B5 between A4 and A5). Used for posters, books, envelopes.
- C series – envelope sizes designed to fit A series (e.g., C4 fits A4 unfolded, C5 fits A5).
All dimensions are rounded to the nearest millimetre. This calculator uses exact formulas for precise values.
Common ISO Sizes (mm)
| Size | Width | Height | Area (m²) |
|---|---|---|---|
| A0 | 841 | 1189 | 1.000 |
| A1 | 594 | 841 | 0.500 |
| A2 | 420 | 594 | 0.250 |
| A3 | 297 | 420 | 0.125 |
| A4 | 210 | 297 | 0.0625 |
| A5 | 148 | 210 | 0.0313 |
| B4 | 250 | 353 | 0.088 |
| B5 | 176 | 250 | 0.044 |
Frequently Asked Questions
Is US Letter the same as A4?
No, US Letter is 8.5×11 inches (216×279 mm). A4 is 210×297 mm – slightly narrower and taller.
What is the aspect ratio of ISO sizes?
All ISO A, B, C series have an aspect ratio of √2 : 1 (≈1.414). This allows scaling from one size to another without distortion.
How many A4 sheets in A0?
A0 = 1 m², A4 = 1/16 m², so 16 A4 sheets make one A0 (2⁴).