File Checksum Calculator

What this tool does

File Checksum Calculator streams any number of files of any size through several hash algorithms in one pass. It verifies results against a pasted or loaded checksum list in GNU or BSD format and exports manifests as sha256sum-compatible text, BSD tags, CSV or JSON.

Software projects publish checksums so you can confirm that the installer or disk image you downloaded is byte-for-byte what they released, not a corrupted or tampered copy. Linux distributions ship a SHA256SUMS file covering dozens of images, backup jobs need a manifest to prove archives are intact years later, and forensic work requires a record of hashes taken at acquisition.

This calculator reads each file in 4 MB chunks and updates every selected algorithm from the same chunk, so a 10 GB image is read once even if you want MD5, SHA-256 and BLAKE3 together. Paste the contents of a checksum list, or drop the .sha256 or .md5 file, and each file is matched by name and marked OK or FAILED. It understands GNU lines (hash, two spaces, filename), the binary-mode asterisk, BSD tagged lines and SFV. Files never leave your computer.

How to use File Checksum Calculator

1. Tick the algorithms you need in the Algorithms panel; SHA-256 is selected by default.
2. Drop one or more files on “Drop files to checksum”. Progress and throughput appear as they are read.
3. To check a single download, paste the published value into “Expected hash for a single file”.
4. To check many files, paste a list into Checksum list or use “Or load a checksum file”.
5. Read the OK and FAILED badges and the summary of verified, failed and missing files.
6. Under Export choose GNU, BSD tagged, CSV or JSON and download the manifest.

Tips for better results

• Verify the checksum file itself. Projects often sign SHA256SUMS with GPG; a checksum served from the same compromised server proves little on its own.
• Matching is by filename without folders, so renamed downloads (for example “image (1).iso”) need renaming or the single-hash field.
• BLAKE3 and XXH64 are several times faster than SHA-256 for building your own large backup manifests.
• Use the GNU export to verify later on Linux or macOS with sha256sum -c checksums.sha256 or shasum -a 256 -c.

Common use cases

• Confirming an operating-system ISO before writing it to a USB stick.
• Creating a manifest of photos or documents before archiving, then re-checking it later.
• Recording evidence hashes in a chain-of-custody log.
• Checking that a large file copied to a NAS or cloud drive arrived intact.

Common mistakes to avoid

• Comparing against the checksum for a different version or architecture of the same download.
• Relying on MD5 or SHA-1 when the publisher offers SHA-256; collisions can be crafted for the older algorithms.
• Assuming a FAILED result means tampering. Incomplete downloads are a far more common cause, so download again first.