CONVERT
PGM → ICO
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Fast, secure PGM to ICO conversion. No registration required.
PGM is the plain-text grayscale portable map format used in image processing. Reaching a ICO from there is one hop. A PGM → ICO operation is one of the simplest image jobs there is: same pixel grid, different wrapper. What genuinely changes is how lossy the codec is, whether alpha survives, and how large the final file ends up. KaijuConverter picks safe defaults for each of those and lets you override them under Advanced. In practice PGM is the plain-text grayscale portable map format used in image processing. On the other end, ICO is the Windows icon container with multiple resolutions packed into one file.
PGM Grayscale Image
Source formatPGM (Portable Graymap) stores grayscale images in a simple ASCII or binary format.
ICO Icon
Target formatICO is the icon file format used for favicons and Windows application icons. A single ICO file can contain multiple image sizes and color depths for different display contexts.
Why convert PGM to ICO
The real reason to move from PGM to ICO is almost never picture quality — both raster formats store essentially the same pixels. It is about the tools downstream: which editors open the file natively, which CMSes upload it without transcoding, which social platforms accept it. Picking ICO solves those edge cases at the cost of a short conversion step.
HOW TO CONVERT
PGM → ICO
Provide the PGM
Click or drag to upload. We accept a single PGM file per job, with an optional queue of additional images for batch mode.
Encode to ICO
The conversion decodes the PGM, resolves the colour space to sRGB and writes the ICO container around the pixel data.
Save the ICO
The download is streamed back over HTTPS. If you uploaded multiple files, a ZIP with all ICO outputs is produced instead.
Common Use Cases
Share across platforms
Send ICO files to anyone without worrying about whether they have the right software for PGM.
Embed in documents
Drop ICO output into Word, Google Docs, PowerPoint, Notion or a website without conversion warnings.
Optimize size
ICO often produces smaller files than PGM for web, email and storage.
Archive & future-proof
Store in a widely-supported format that will still open on future operating systems without legacy plugins.
PGM vs ICO — Strengths and limitations
What each format does best, and where it falls short.
PGM Strengths
- Trivially simple to parse and generate.
- Ideal Unix pipeline intermediate for grayscale processing.
- Preserves 16-bit depth for scientific and medical data.
- Universal tooling (Netpbm, ImageMagick, Tesseract).
- ASCII variant is human-readable.
Limitations
- No compression — files balloon for large images.
- No metadata, no color profile.
- Grayscale only — drop to PBM for bitmap or up to PPM for color.
ICO Strengths
- Multi-resolution: one file, many sizes, OS picks the right one.
- Universal favicon support in every browser since IE5.
- Supports transparency (1-bit since 1985, full alpha since XP).
- Tiny file size — an entire favicon pack typically fits in under 15 KB.
- No licensing or patent concerns — fully in the public domain spec-wise.
Limitations
- Cannot compress continuous-tone images efficiently — use PNG or WebP for photos.
- Format is essentially frozen in 1999 — no HDR, no wide gamut, no modern features.
- Maximum image dimension is 256×256 px (inside an ICO container).
PGM vs ICO — Technical specifications
Side-by-side comparison of the technical details.
PGM
- MIME type
- image/x-portable-graymap
- Extension
- .pgm
- Variants
- P2 (ASCII), P5 (binary)
- Bit depth
- 8-bit or 16-bit per pixel
- Creator
- Jef Poskanzer (1988), Netpbm toolkit
ICO
- MIME type
- image/vnd.microsoft.icon
- Max resolutions per file
- 65 535 images
- Max single image size
- 256×256 px
- Color depths
- 1, 4, 8, 24, 32 bits per pixel
- Compression
- Uncompressed bitmap or embedded PNG (Vista+)
| Specification | PGM | ICO |
|---|---|---|
| MIME type | image/x-portable-graymap | image/vnd.microsoft.icon |
| Extension | .pgm | — |
| Variants | P2 (ASCII), P5 (binary) | — |
| Bit depth | 8-bit or 16-bit per pixel | — |
| Creator | Jef Poskanzer (1988), Netpbm toolkit | — |
| Max resolutions per file | — | 65 535 images |
| Max single image size | — | 256×256 px |
| Color depths | — | 1, 4, 8, 24, 32 bits per pixel |
| Compression | — | Uncompressed bitmap or embedded PNG (Vista+) |
PGM vs ICO — Typical file sizes
Approximate file sizes for common scenarios.
PGM
- 1920×1080 grayscale 8-bit (binary P5) ~2 MB
- 1920×1080 grayscale 16-bit ~4 MB
- DICOM-equivalent medical slice 500 KB - 20 MB
ICO
- Classic favicon (16×16 only) < 2 KB
- Multi-size favicon pack (16/32/48/256) 5-15 KB
- Full Windows app icon set 20-100 KB
Quality & Compatibility
PGM-to-ICO conversion does not change the visible content. Quality is capped by the PGM decode; re-encoding a lossy source at high quality cannot recover detail that was already discarded. For archival masters, keep the original PGM alongside the ICO copy.
Tips for Best Results
- Large PGM files may look identical to small ICO files for photographic content; pick quality based on end use, not headline megapixels.
- For print, export ICO at 300 DPI minimum and check that the colour profile embedded matches the print shop specification.
- Batch-convert related PGM images in one pass so they share identical encoder settings and look consistent side-by-side.
Frequently Asked Questions
It depends on the codecs involved. If both PGM and ICO are lossy, the pixels are re-encoded and a small amount of detail is discarded — invisible at default quality settings on photographs. If ICO is lossless (PNG, TIFF, BMP) the output keeps every pixel of the decoded PGM exactly, but cannot recover detail that PGM had already compressed away.
Often yes, especially when ICO is lossless. PGM tuned for efficient web delivery will usually produce smaller files than ICO's default settings. If file size matters, drop the quality in Advanced or pick a more compressed target format instead.
KaijuConverter uploads over HTTPS, processes the image in an isolated container and deletes both the source and the output within two hours. No account is required, file contents are never logged, and we do not use uploads to train any model. For confidential material, the paid plan includes a data-processing agreement.
Related comparisons
See these formats side by side to understand which fits your use case best.
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Read guideSecure & Private Conversion
Your files are encrypted during transfer, processed in isolated containers, and automatically deleted within 60 minutes. We never read, share, or store your data.