Steganography Capacity Calculator
Calculate exact hidden-payload capacity for PNG, BMP, WebP, WAV, FLAC, AIFF and more — plus PSNR and detection risk, all client-side. Links to the right specialist hider/extractor for your file type.
100% client-side — no file ever leaves your browser.
Drop a file to check its real capacity
PNG, BMP, WebP, GIF, JPEG, TIFF, WAV, MP3, PDF, DOCX, SVG, and more — up to 50 MB
Don't have a file yet?
How to Use the Capacity Calculator (5 steps)
- Type a width and height — see instant capacity, PSNR, and detection risk for every bit depth, no upload needed
- Or drop a real file — auto-detects the format and computes exact (or estimated) capacity for PNG, WAV, JPEG, and more
- Drop a second file to check whether it actually fits — get the minimum image size if it doesn't
- Switch to Standard/Forensic mode for the reverse calculator — find the minimum image size for a payload you need to hide
- Follow the CTA to the correct specialist hider/extractor for your exact file type — this calculator never hides or extracts data itself
Capacity by Format — What's Exact vs. Estimated
| Format | Method | Precision | Notes |
|---|---|---|---|
| PNG / BMP / TIFF / WebP (lossless) | Exact capacity formula | ✅ Exact | Full (W×H×channels×bits/8) |
| WAV (PCM) | Exact capacity + SNR | ✅ Exact | Full (samples×channels×bits/8) |
| JPEG | DCT coefficient estimate | ⚠️ ±40% range | Estimate only — needs full decode for exact |
| GIF | Palette-index LSB | ✅ Exact but tiny | Limited (~32B–a few KB) |
| PDF / DOCX / SVG | Metadata / XML fields | ❌ Depends on method | Method-dependent |
Frequently Asked Questions
How is image steganography capacity calculated?
For LSB (Least Significant Bit) steganography on PNG, BMP, or lossless WebP: capacity = floor((width × height × channels × bits-per-channel) / 8) − 4 bytes for the length header. RGB images have 3 channels, RGBA has 4.
What does PSNR mean and what's a safe value?
PSNR (Peak Signal-to-Noise Ratio) measures how much a modification distorts an image, in decibels. Above ~40 dB is generally imperceptible to the human eye. 1-bit LSB modification typically gives ~53 dB (imperceptible); 6-bit or 8-bit modification drops well below 30 dB and becomes visibly detectable.
What is detection risk (BPP) and where do the thresholds come from?
BPP (bits per pixel) measures how much of an image's capacity your payload actually uses. This tool uses the Fridrich & Goljan steganalysis research thresholds: BPP < 0.005 is statistically undetectable by RS-analysis/chi-square, BPP < 0.05 is only detectable by specialized tools, and BPP ≥ 0.687 is reliably detectable by any steganalysis method.
Why is JPEG capacity only an estimate?
JPEG steganography hides data in DCT (Discrete Cosine Transform) coefficients created during compression, not raw pixels. The exact count of usable (non-zero AC) coefficients depends on image content and JPEG quality, and can only be known by actually decoding the JPEG — this calculator gives a ±40% estimate based on typical coefficient density.
Why does PDF/DOCX/SVG show 'depends on method' instead of one number?
Unlike pixel-based image formats, these are structured documents — capacity depends entirely on which hiding technique you choose (metadata field, custom XML part, comment injection, etc.), each with a very different practical size limit.
Is my file uploaded anywhere?
No. Every calculation runs entirely in your browser using a Web Worker — nothing is ever sent to a server. You can verify this by checking your browser's network tab during use.
Why doesn't this tool actually hide or extract data?
This page answers one question — how much can I hide, and how safely — then routes you to the correct specialist tool for your exact file type and method. Each specialist hider/extractor (Image, WAV, JPEG, GIF, PDF, Document, SVG, MP3) already has the full feature set for that format — encryption, algorithm choice, batch tools, and more — so this calculator doesn't duplicate a smaller version of them.
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