Open an image. Set the scale. Measure.
Windows · Linux · macOS · Quick guide · Python examples
Windows · Linux · macOS · Portable · No installer
lengto measures real distances on scanned plans, technical photographs and microscope images. All you need is a known reference length. Use a single EXE on Windows, an AppImage on Linux, or an app bundle on macOS.
Application render using a synthetic drawing.
| System | Download | First start |
|---|---|---|
| Windows 10/11, x64 | lengto.exe | Double-click. No installation. |
| Linux, x86_64 | AppImage | Allow execution in the file properties, then double-click. |
| macOS 11+, Intel and Apple Silicon | Universal app ZIP | Extract and open lengto.app; moving it to Applications is optional. |
Linux and macOS are preview builds, tested automatically on Ubuntu and both Mac architectures. On macOS, the app is ad-hoc signed and is not notarized; the first launch may require System Settings → Privacy & Security → Open Anyway. On Linux without FUSE, use ./lengto-linux-x86_64.AppImage --appimage-extract-and-run.
Setup details and optional Python support →
- Open or paste. TIFF, PNG, JPEG and PDF, including multipage documents. Paste images with Ctrl+V (Command+V on macOS).
- Calibrate and measure. Pixel snapping, flexible units and editable measurement labels.
- Save the result. Export annotated images or PDFs; include all pages in TIFF/PDF.
- Repeat the work. Record editable Python macros and apply them to other images or whole folders.
- Choose the package for your system, then open, drop or paste an image.
- Choose Measurements → Calibrate, enter a known length and click its endpoints.
- Choose Measure, click endpoint pairs, then File → Export to save. Esc ends the tool.
Every recorded point keeps its pixel coordinates, relative position and source color. Edit the macro to find colored features, repeat measurements or process a folder. Relative coordinates adapt to resized images with matching framing; RGB searches let your script choose new endpoints.
Python 3.8+ is needed only to run macros. Measuring and recording need nothing extra.
Know the limits: one uniform scale per document; no perspective correction. Exports flatten annotations and use preview resolution. Keep the source and a macro to reproduce your work.
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MIT license · © 2026 Ivan Panzera. Bundled components retain their own licenses.