JPEG File Size Calculator: Quality vs File Size
Estimate JPG file size from megapixels and quality (1–100). See the KB at Q60, Q75, Q85, Q90 and Q100 with a full compression table. Free, instant.
See step-by-step calculation
When to use this calculator
- Choosing the JPEG quality before uploading product photos so each one lands under Google's recommended ~200 KB per hero image.
- Estimating how many 12 MP vacation photos fit on a 32 GB SD card at Q=75 vs Q=90 before a trip.
- Deciding whether to export a 24 MP DSLR portrait at Q=75 or Q=90 to stay under a 1 MB email attachment cap.
- Sizing a news site's hero images to meet a Core Web Vitals LCP target under 2.5 s on 4G.
JPEG Compression Ratio & File Size by Quality Setting
| Quality (Q) | Compression Ratio | Estimated Size (2 MP) | Estimated Size (12 MP) | Visual Loss | Typical Use Case |
|---|---|---|---|---|---|
| Q = 100 | ~3:1 | ~1.91 MB | ~11.4 MB | Imperceptible | Archival, print pre-press |
| Q = 95 | ~5:1 | ~1.17 MB | ~7.0 MB | Imperceptible | Photography masters |
| Q = 90 | ~10:1 | ~586 KB | ~3.4 MB | None to very slight | High-quality web, portfolios |
| Q = 85 | ~15:1 | ~391 KB | ~2.29 MB | None on screen | Web sweet spot |
| Q = 75 | ~22:1 | ~266 KB | ~1.56 MB | Slight on close-up | General web, blog images |
| Q = 60 | ~35:1 | ~167 KB | ~1.0 MB | Noticeable artifacts | Thumbnails, social previews |
| Q = 40 | ~50:1 | ~117 KB | ~703 KB | Visible blocking | Low-bandwidth delivery |
| Q = 20 | ~80:1 | ~73 KB | ~439 KB | Severe degradation | Placeholder / blur previews |
Fuente: hacecuentas.com – JPEG File Size Calculator (model: MP × 3,000,000 ÷ compression ratio ÷ 1024). Sizes are estimates for typical photographic content; high-entropy scenes (dense foliage, textures) may exceed these values significantly.
How it works
How JPEG File Size Is Calculated
JPEG file size depends on three things: the pixel count, the color depth, and the quantization aggressiveness set by the quality slider. The practical estimate is:
Raw Bytes = Megapixels × 1,000,000 × 3 (3 bytes/pixel, 8-bit RGB)
JPEG Bytes = Raw Bytes ÷ Compression_Ratio(Q)
KB = JPEG Bytes ÷ 1024The whole game is the compression ratio, and it changes dramatically with the quality setting.
Compression Ratio by Quality
| Quality (Q) | Compression Ratio | Visual Loss | Typical Use Case |
|---|---|---|---|
| 100 | ~3:1 | Imperceptible | Archival, print pre-press |
| 95 | ~5:1 | Imperceptible | Photography masters |
| 90 | ~10:1 | None to very slight | High-quality web, portfolios |
| 85 | ~15:1 | None on screen | The web sweet spot |
| 75 | ~22:1 | Slight on close-up | General web, blog images |
| 60 | ~35:1 | Noticeable artifacts | Thumbnails, social previews |
| 40 | ~50:1 | Visible blocking | Low-bandwidth delivery |
| 20 | ~80:1 | Severe degradation | Placeholder / blur previews |
> Why it matters: going from Q=100 to Q=85 multiplies the compression ratio 5× (3:1 → 15:1), so the file shrinks ~80% while the difference is invisible at screen resolution. That single change is the highest-leverage image optimization on the web.
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JPEG Size Reference Table (by megapixels & quality)
Estimated file size for natural-photo content, matching the calculator's model:
| Megapixels | Resolution Example | Q=100 | Q=90 | Q=85 | Q=75 | Q=60 |
|---|---|---|---|---|---|---|
| 0.3 MP | 640 × 480 | ~293 KB | ~88 KB | ~59 KB | ~40 KB | ~25 KB |
| 2 MP | 1920 × 1080 (FHD) | ~1.91 MB | ~586 KB | ~391 KB | ~266 KB | ~167 KB |
| 8 MP | 3264 × 2448 | ~7.6 MB | ~2.29 MB | ~1.53 MB | ~1.04 MB | ~668 KB |
| 12 MP | 4000 × 3000 | ~11.4 MB | ~3.4 MB | ~2.29 MB | ~1.56 MB | ~1.0 MB |
| 24 MP | 6000 × 4000 | ~22.9 MB | ~6.9 MB | ~4.58 MB | ~3.1 MB | ~2.0 MB |
| 50 MP | 8688 × 5792 | ~47.7 MB | ~14.3 MB | ~9.5 MB | ~6.5 MB | ~4.2 MB |
These are estimates for typical photographic content. A 24 MP photo of a clear sky can compress to under 1 MB at Q=85, while the same 24 MP shot of dense foliage may exceed 6 MB — content entropy is the dominant variable.
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Worked Cases
Case 1 — E-commerce product photo (2 MP, Q=85). Raw = 2,073,600 px × 3 ≈ 6 MB. At ~15:1: ≈ 390 KB output. Within most PageSpeed budgets for a hero image; convert to WebP to drop another 25–35%.
Case 2 — Smartphone photo for Instagram (12 MP, Q=75). 12 M × 3 ÷ 22 ÷ 1024 ÷ 1024 ≈ 1.56 MB. Instagram recompresses uploads to ~85–500 KB and caps the long edge at 1080 px, so pre-shrinking avoids a double-compression penalty.
Case 3 — Archival document scan (8 MP, Q=95). 8 M × 3 ÷ 5 ÷ 1024 ÷ 1024 ≈ 4.6 MB. For archival or OCR, Q=90–95 preserves fine text edges.
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Common Mistakes
1. Using Q=100 for web. Q=100 produces files 5–8× larger than Q=85 with differences invisible at 96 PPI. The browser can't display the extra fidelity.
2. Mixing up quality scales. Photoshop's 0–12 scale ≠ libjpeg's 0–100. Photoshop "10" ≈ libjpeg Q=85; Photoshop "12" ≈ Q=97. Compare output bytes, not the slider number.
3. Ignoring content type. JPEG is bad at flat color, text, and line art — PNG or WebP can be 60–80% smaller for those. JPEG shines on continuous-tone photos.
4. Re-saving repeatedly. Every save below Q=100 re-applies lossy compression; artifacts and file size creep up 5–15% per cycle. Always edit from a lossless master (RAW/PNG).
5. Assuming size scales only with megapixels. Content entropy matters as much as resolution — a smooth scene at 24 MP can beat a textured scene at 12 MP.
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Related Calculators
Worked Example: 12 MP photo at Q=85
Frequently asked questions
What JPEG quality should I use for website images?
How big is a 12 MP photo as a JPEG?
How does megapixel count affect JPEG file size?
Why does Q=100 produce such a huge file?
Is JPEG compression lossy? Can I recover the original?
What is the difference between Q=85 in Photoshop and libjpeg?
Why is my JPEG sometimes larger after re-saving at the same quality?
Does JPEG quality affect color accuracy?
How much smaller is WebP than JPEG at the same quality?
What quality do smartphones and social networks use?
Sources & references
Methodology & trust
Calculadora de tecnología revisada por el equipo editorial de Hacé Cuentas, contrastada con Wikipedia – JPEG (compression, quantization & quality), según nuestra política editorial y metodología.
Última revisión: June 20, 2026. Los parámetros se verifican periódicamente con las fuentes citadas.
Calculations run 100% in your browser. We do not store or transmit your data.
Indicative results. For critical decisions, consult a professional.
Rodríguez, M. (2026). JPEG File Size Calculator: Quality vs File Size. Hacé Cuentas. https://hacecuentas.com/jpg-quality-size-web-optimization
Contenido bajo licencia CC-BY 4.0 — reutilizable citando la fuente con enlace a Hacé Cuentas.