A-Series Paper Size
A0 is 841 × 1189 mm, an area of exactly one square metre. Each step up the number halves the long side, so A4 lands at 210 × 297 mm.
Your numbers
Length
297mm
Width
210mm
Area
623.7cm²
Formula
Length = 1189 ÷ 2^(⌈A-series number÷2⌉), Width = 841 ÷ 2^(⌊A-series number÷2⌋)
The 1:√2 side ratio is what lets the proportions survive every fold in half.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| A-series numberThe number in an A size; each step up halves the sheet. | 4 | 0 ~ 10 |
Step by step
Quick reference table
Results when only A-series number changes and everything else stays put.
| A-series number | Length (mm) | Width (mm) | Area (cm²) |
|---|---|---|---|
| 2 | 594 | 420 | 2,494.8 |
| 3 | 420 | 297 | 1,247.4 |
| 4 | 297 | 210 | 623.7 |
| 6 | 148 | 105 | 155.4 |
| 8 | 74 | 52 | 38.5 |
What each result means
| Result | At default values |
|---|---|
| Length (mm)The measurement across, side to side. | 297 |
| Width (mm)The measurement front to back. | 210 |
| Area (cm²)The space a shape covers — length squared. | 623.7 |
Common mistakes
The 1:√2 side ratio is what lets the proportions survive every fold in half.
Glossary
- A-series number
- The number in an A size; each step up halves the sheet.
- Length
- The measurement across, side to side.
- Width
- The measurement front to back.
- Area
- The space a shape covers — length squared.
Frequently asked questions
Q. How is A-Series Paper Size calculated?
Length = 1189 ÷ 2^(⌈A-series number÷2⌉), Width = 841 ÷ 2^(⌊A-series number÷2⌋) — A0 is 841 × 1189 mm, an area of exactly one square metre. Each step up the number halves the long side, so A4 lands at 210 × 297 mm.
Q. Can you walk through an example?
With A-series number 4, the answer is Length 297mm.
Q. What do I need to enter?
Enter A-series number. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only A-series number moves the answer to A-series number 2 → Length (mm) 594 and A-series number 8 → Length (mm) 74. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
The 1:√2 side ratio is what lets the proportions survive every fold in half.
Related calculators
Keep your length units consistent across inputs — mixing centimetres and metres throws results far off.