CSCalc

Sysex Checksum Calculator

Calculate checksums for

• Additive type checksums (2's Complement).

  • This includes Roland/Yamaha

• Additive type checksums (1's Complement).

• Simple Summing (additive) AND 0x7f

• SONY checksums MSB

• XOR checksums

  • Many manufacturers also use this system.

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Paste in a sysex string and enter the start byte for the data.
The end byte can either be determined using the subsequent bytes from start or determined by counting back from the end.

Example. To calculate the Roland checksum for the sysex string:

f0 41 10 57 12 03 00 01 10 31 00 f7

The checksum (0x3B) can be calculated by entering in:

• Start Byte Index=5 : End Offset =2 03 00 01 10 31
• Start Byte Index=5 : Length =5 03 00 01 10 31

CHANGELOG

• Version v7.0 - 08/17/2025
  • Can now send MIDI out of corrected checksum message
• Version v6.0 - 08/16/2025
  • Changed name from Sysex Checksum Calculator to CSCalc
  • Changed logo
• Version v5.1 - 08/09/2025
  • removed Kawai K5 checksum code
• Version v5.0 - 08/08/2025
  • Slight refactor of Roland checksum
  • Added Kawai K5(m) checksum
• Version v4.0 - 08/07/2025
  • Using Slider() for star/end parameters
  • Added SONY MSB checksum
• Version v3.0.0 - 08/07/2025
  • Changed to lighter theme
  • Added 1's complement checksum
  • Added Simple summing checksum
  • Moved sysex input window to main window for easier editing.
• Version v2.0.0 - 08/05/2025
  • Ctrl+click to copy sysex message only to buffer
  • Print out result now prints checksum
• Version v1.0.0 - 08/04/2025
  • first release