✉️ C5 Envelope
| Millimeters | 162 × 229 mm |
| Centimeters | 16.2 × 22.9 cm |
| Inches | 6.38 × 9.02 in |
| Points | 459 × 649 pt |
| Picas | 38.3 × 54.1 pc |
| Pixels (300dpi) | 1913 × 2705 px |
| Pixels (72ppi) | 459 × 649 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 C4 = 2 × C5 (double the area). Scaling factor: √2 ≈ 1.4142 per side.
C4 is the standard business envelope size for A4 documents — this tool helps you scale up from C5 for professional mail and correspondence.
C4 (area) = C5 × 0.5 · Scale factor = √2 ≈ 1.4142 per side1 C4 sheet has twice the area of 1 C5 sheet.
📏 What is C5 Envelope Size?
C5 is a medium envelope size in the ISO 216 C-series. Its dimensions are 162 × 229 mm (6.4 × 9.0 inches), with an area of 0.037 m². C5 is designed to hold A5 paper without folding (A5 is 148 × 210 mm). It's commonly used for professional mail, invitations, flyers, and small-format correspondence. C5 is exactly half the area of C4, making it a popular choice for compact mail and invitations.
📄 What is C4 Envelope Size?
C4 is a medium-large 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 double the area of C5, making it the most common professional envelope size worldwide.
🧮 The Math: How C5 Becomes C4
The ISO 216 C-series is based on the geometric mean of the A and B-series. Each step up (C5 → C4) doubles the area. The side lengths increase by a factor of √2 ≈ 1.4142.
- Width: 162 mm × √2 ≈ 229 mm
- Height: 229 mm × √2 ≈ 324 mm
- Area: 0.037 m² × 2 = 0.074 m²
Formula: 1 C4 = 2 × C5 (in area). So, if you have 2 C5 envelopes, they can be combined to form 1 C4 envelope (or 1 C5 = 0.5 C4).
📊 Quick Conversion Table: C5 to C4
| C5 Envelopes | C4 Equivalent | Scale factor (side) | Real‑world use |
|---|---|---|---|
| 0.5 C5 | 0.25 C4 | 100% (C5 = half C4) | Small invitation |
| 1 C5 | 0.5 C4 | 141.4% (enlarge) | Single invitation, flyer |
| 2 C5 | 1 C4 | 200% (double width/height) | Business envelope, A4 mail |
| 4 C5 | 2 C4 | 282.8% | Two business envelopes |
| 5 C5 | 2.5 C4 | 316.2% | Bulk mailing |
| 10 C5 | 5 C4 | 447.2% | Large mailing campaign |
| 25 C5 | 12.5 C4 | 707.1% | Marketing mailer |
| 50 C5 | 25 C4 | 1000% | Large-scale mail |
✉️ Real‑World Examples: C5 to C4 in Action
- 📦 Professional Mail: C5 is used for invitations and small flyers. 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 C5 envelope.
- 💌 Invitations & Announcements: C5 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: C5 flyers and invitations can be designed, and then the same artwork can be scaled to C4 for larger-format mailers or handouts.
- 🏢 Office Correspondence: C4 is the standard for business letters and official documents. C5 is used for smaller correspondence and invitations. Convert between them for consistent document management.
- 🖨️ Printing & Production: Understanding C5 to C4 conversion is essential for print production, especially when printing multiple envelope sizes from the same sheet.
💡 Professional Tips for C5 to C4 Scaling
🎯 Resolution & Quality
When scaling from C5 to C4, if your original is 300 DPI, the resulting C4 will be ~212 DPI — still acceptable for most printing. For high-quality prints, design at 600 DPI at C5 to get ~424 DPI at C4.
📐 C‑Series vs. A‑Series
C-series envelopes are designed to fit A-series paper. C5 is designed to hold A5 paper (148 × 210 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 C5 invitations from 1 C4 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 (C5 to C4)
Q: How many C4 envelopes equal 1 C5?
A: Exactly 2 C5 envelopes make 1 C4 in terms of area. You can fit two C5 envelopes on one C4 sheet.
Q: What is the scaling factor from C5 to C4?
A: Each side is scaled by √2 ≈ 1.4142, meaning you enlarge the width and height by 41.4%.
Q: Can I fit a C5 document into a C4 envelope?
A: Yes, by scaling it up to 141.4% on each dimension. The document will fit, with more white space around it.
Q: What is the difference in area between C5 and C4?
A: C4 has exactly double the area of C5 (0.074 m² vs. 0.037 m²).
Q: Is C5 bigger than C4?
A: No, C4 is larger. C4 is the next size up from C5. 1 C4 = 2 × C5.
Q: What is C5 used for?
A: C5 is used for invitations, flyers, small-format correspondence, and compact mail.
Q: What is C4 used for?
A: C4 is used for business mail, official documents, standard invitations, and professional correspondence.
Q: Can I print C5 on C4?
A: Yes, by scaling up to 141.4%. 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 C5‑to‑C4 Conversion Matters
Accurate scaling between C5 and C4 is essential for professional mail, envelope production, and document management. Whether you're preparing an invitation, designing a flyer, 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 = 162 × 229 mm – medium envelopes, invitations, 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 C5, C4 to C3, C3 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.