✉️ C3 Envelope
| Millimeters | 324 × 458 mm |
| Centimeters | 32.4 × 45.8 cm |
| Inches | 12.76 × 18.03 in |
| Points | 918 × 1298 pt |
| Picas | 76.5 × 108.2 pc |
| Pixels (300dpi) | 3827 × 5410 px |
| Pixels (72ppi) | 918 × 1298 px |
✉️ C4 Envelope
| Millimeters | 229 × 324 mm |
| Centimeters | 22.9 × 32.4 cm |
| Inches | 9.02 × 12.76 in |
| Points | 649 × 918 pt |
| Picas | 54.1 × 76.5 pc |
| Pixels (300dpi) | 2705 × 3827 px |
| Pixels (72ppi) | 649 × 918 px |
Area: 1 C3 = 2 × C4 (C4 is half the area). Scaling factor: 1/√2 ≈ 0.7071 per side.
C4 is the standard business envelope size for A4 documents — this tool helps you scale down from C3 for professional mail and correspondence.
C4 = C3 × 2 · Scale factor = 1/√2 ≈ 0.7071 per side1 C3 envelope splits into exactly 2 C4 envelopes (or 1 C4 = 0.5 C3).
📏 What is C3 Envelope Size?
C3 is a large envelope size in the ISO 216 C-series. Its dimensions are 324 × 458 mm (12.8 × 18.0 inches), with an area of 0.148 m². C3 is designed to hold A3 paper without folding (A3 is 297 × 420 mm). It's commonly used for professional mail, catalogs, large-format correspondence, and oversized invitations. C3 is exactly double the area of C4, making it the ideal size for large documents, presentations, and bulk mailings.
📄 What is C4 Envelope Size?
C4 is a medium envelope size in the ISO 216 C-series. Its dimensions are 229 × 324 mm (9.0 × 12.8 inches), with an area of 0.074 m². C4 is designed to hold A4 paper without folding (A4 is 210 × 297 mm). It's the standard envelope size for professional correspondence, business mail, and official documents. C4 is exactly half the area of C3, making it the most common professional envelope size worldwide.
🧮 The Math: How C3 Becomes C4
The ISO 216 C-series is based on the geometric mean of the A and B-series. Each step down (C3 → C4) halves the area. The side lengths decrease by a factor of 1/√2 ≈ 0.7071.
- Width: 324 mm × (1/√2) ≈ 229 mm
- Height: 458 mm × (1/√2) ≈ 324 mm
- Area: 0.148 m² ÷ 2 = 0.074 m²
Formula: 1 C3 = 2 × C4 (in area). So, if you have 1 C3 envelope, you can create 2 C4 envelopes from it (or 1 C4 = 0.5 C3).
📊 Quick Conversion Table: C3 to C4
| C3 Envelopes | C4 Equivalent | Scale factor (side) | Real‑world use |
|---|---|---|---|
| 0.5 C3 | 1 C4 | 100% | Single business envelope |
| 1 C3 | 2 C4 | 70.7% (reduce) | Two business envelopes |
| 2 C3 | 4 C4 | 50% (half width/height) | Four professional envelopes |
| 5 C3 | 10 C4 | 31.6% | Bulk mailing |
| 10 C3 | 20 C4 | 22.4% | Large mailing campaign |
| 25 C3 | 50 C4 | 14.1% | Marketing mailer |
| 50 C3 | 100 C4 | 10% | Large-scale mail |
| 100 C3 | 200 C4 | 7.1% | Massive mailing |
✉️ Real‑World Examples: C3 to C4 in Action
- 📦 Professional Mail: C3 is used for large catalogs and oversized invitations. When you need to produce standard C4 business envelopes for regular correspondence, this converter tells you exactly how many C4 envelopes you can create from each C3 envelope.
- 💌 Invitations & Announcements: C3 is often used for premium invitations and announcements. C4 is used for standard reply envelopes and thank-you notes. Understanding the scaling helps with consistent branding.
- 📬 Marketing Materials: C3 flyers and catalogs can be designed, and then the same artwork can be scaled to C4 for smaller-format mailers or handouts.
- 🏢 Office Correspondence: C4 is the standard for business letters and official documents. C3 is used for larger presentations and reports. Convert between them for consistent document management.
- 🖨️ Printing & Production: Understanding C3 to C4 conversion is essential for print production, especially when printing multiple envelope sizes from the same sheet.
💡 Professional Tips for C3 to C4 Scaling
🎯 Resolution & Quality
When scaling from C3 to C4, if your original is 300 DPI, the resulting C4 will be ~424 DPI — actually higher quality! This is because you're concentrating the same pixels into a smaller area. For best results, design at 300 DPI at C3 for sharp C4 prints.
📐 C‑Series vs. A‑Series
C-series envelopes are designed to fit A-series paper. C3 is designed to hold A3 paper (297 × 420 mm) without folding. C4 holds A4 paper (210 × 297 mm) without folding. This makes C4 the most common business envelope size.
💰 Printing & Mailing Efficiency
Printing 2 C4 envelopes from 1 C3 sheet can save paper and costs. Many professional printers support C-series sizes — check your printer settings for "scale to fit" options.
📂 Professional Correspondence
C4 is the standard for business mail, official documents, and professional correspondence. Use this converter to plan your envelope sizes for professional communications.
❓ Frequently Asked Questions (C3 to C4)
Q: How many C4 envelopes equal 1 C3?
A: Exactly 2 C4 envelopes make 1 C3 in terms of area. You can fit two C4 envelopes on one C3 sheet.
Q: What is the scaling factor from C3 to C4?
A: Each side is scaled by 1/√2 ≈ 0.7071, meaning you reduce the width and height by 29.3%.
Q: Can I fit a C3 document into a C4 envelope?
A: Yes, by scaling it down to 70.7% on each dimension. The document will fit, but text and details will be smaller.
Q: What is the difference in area between C3 and C4?
A: C3 has exactly double the area of C4 (0.148 m² vs. 0.074 m²).
Q: Is C3 bigger than C4?
A: Yes, C3 is larger. C3 is the next size up from C4. 1 C3 = 2 × C4.
Q: What is C3 used for?
A: C3 is used for large catalogs, oversized invitations, professional mail, and large-format correspondence.
Q: What is C4 used for?
A: C4 is used for business mail, official documents, standard invitations, and professional correspondence.
Q: Can I print C3 on C4?
A: Yes, by scaling down to 70.7%. Most printers support this scaling. This tool helps you understand the exact ratio.
Q: What is the C‑series used for?
A: C‑series envelopes are designed for flat mail and professional correspondence, holding A‑series paper without folding.
📈 Why Accurate C3‑to‑C4 Conversion Matters
Accurate scaling between C3 and C4 is essential for professional mail, envelope production, and document management. Whether you're preparing a catalog, designing an invitation, or planning a mailing campaign, this tool ensures your envelopes fit perfectly every time. Inaccurate scaling can lead to wasted paper, misaligned designs, and costly reprints.
🌐 Global Standards & Professional Usage
The C‑series (ISO 216) is used alongside the A‑series and B‑series in many countries. C‑series envelopes are specifically designed for flat mail and professional correspondence. C4 is the most widely used business envelope size globally. This tool supports professional envelope size conversions for users worldwide.
📐 The Full C‑Series Hierarchy
- C8 = 64 × 91 mm – small correspondence
- C7 = 91 × 128 mm – small envelopes, invitations
- C6 = 128 × 182 mm – standard envelopes, invitations
- C5 = 182 × 257 mm – medium envelopes, flyers
- C4 = 229 × 324 mm – standard mail, A4 documents, business envelopes
- C3 = 324 × 458 mm – large mail, catalogs, A3 documents
- C2 = 458 × 648 mm – oversized mail, A2 documents
- C1 = 648 × 917 mm – very large mail, posters
- C0 = 917 × 1297 mm – extremely large mail, display
Each step up doubles the area, making the system intuitive and easy to scale.
🔗 Explore More Envelope & Mail Tools
Check out our other converters: C4 to C3, C4 to C5, C5 to C4, C5 to C6, C6 to C5, DL to C4, and C4 to DL. All designed to make your print and mail workflows smoother.