Septenary (base 7) to decimal converter
Paste a number in septenary (base 7) to get its decimal value, worked out place by place. Handy for exercises and for checking encoded values.
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How to use it
- Enter number in base 7.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Value = sum of (digit × 7^position), with position 0 at the far right. Example: 6666 = 6×7^3 + 6×7^2 + 6×7^1 + 6×7^0 = 2400.
Example
Inputs: Number in base 7 = 6666. Result: Decimal value: 2400; With thousands separators: 2,400; Decimal digits: 4.
6666
2400
Limits and caveats
- Whole numbers only, up to 1000 digits; a radix point is not accepted here.
- The place value table appears for inputs up to 60 digits.
Questions about this tool
How do I convert septenary to decimal by hand?
Multiply each digit by 7 raised to its position, starting at position 0 on the right, then add the results. For example 6666 in base 7 equals 2400.
Why do I get an error when I type the digit 7?
Base 7 digits run from 0 to 6 only, and seven itself is written 10. A 7, 8 or 9 means the input is not a base 7 number.
Which symbols are allowed in base 7?
The digits 0 to 6; spaces are ignored. Any other symbol triggers a message that names it.