A4 ↔ A3 Paper Size Converter
Convert between A4 and A3 paper sizes instantly
📚 A4 ↔ A3 Paper Size Details
A4 to A3 Formula
To convert A4 to A3, divide the number of A4 sheets by 2.
A3 to A4 Formula
To convert A3 to A4, multiply the number of A3 sheets by 2.
Bidirectional Conversion
This converter works both ways simultaneously:
- Type A4 sheets → A3 updates automatically
- Type A3 sheets → A4 updates automatically
- No buttons to click - works as you type
ISO 216 Standard
Both A4 and A3 are part of the ISO 216 paper size standard:
- A4: 210 × 297 mm
- A3: 297 × 420 mm
- Each size is half/double the next
📏 How A4 to A3 Conversion Works
The A-series paper sizes follow a simple geometric progression:
- Area Relationship: A3 has exactly twice the area of A4
- Dimensions: A3 dimensions are √2 times larger than A4 dimensions
- Scale Factor: A3 is 141.4% larger than A4 (√2 ≈ 1.414)
- Real-time: Updates happen as you type, no button clicks required
An dimensions = A(n-1) dimensions × √2
// A4 Dimensions:
Width = 210 mm
Height = 297 mm
// A3 Dimensions:
Width = 210 × √2 = 297 mm
Height = 297 × √2 = 420 mm
// Area Calculation:
A4 Area = 210 × 297 = 62,370 mm²
A3 Area = 297 × 420 = 124,740 mm²
Ratio = 124,740 ÷ 62,370 = 2.0
📊 A4 vs A3 Comparison Table
| Property | A4 Size | A3 Size | Ratio |
|---|---|---|---|
| Dimensions | 210 × 297 mm | 297 × 420 mm | 1:√2 |
| Inches | 8.27 × 11.69" | 11.69 × 16.54" | 1:√2 |
| Area | 62,370 mm² | 124,740 mm² | 1:2 |
| Common Uses | Letters, documents | Posters, drawings | - |
🎯 Practical Applications
Printing & Copying
Calculate how many A4 pages fit on an A3 sheet for booklet printing.
Design & Layout
Scale designs between A4 and A3 while maintaining proportions.
Paper Planning
Estimate paper requirements for printing projects.
Cost Estimation
Compare paper costs between A4 and A3 formats.
❓ Frequently Asked Questions
A: Two A4 sheets equal one A3 sheet. A3 has exactly twice the area of A4.
A: A4 is 210 × 297 mm (8.27 × 11.69 inches). A3 is 297 × 420 mm (11.69 × 16.54 inches).
A: Yes! The scale factor from A4 to A3 is 141.4% (√2). From A3 to A4 it's 70.7% (1/√2).
A: The conversion is mathematically exact based on the ISO 216 standard.