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Digital Infrastructure

Full and Incremental Backup Retention Calculator

How much payload does a fixed set of full backups and incremental days retain?

Measured values and planning assumptions
Supported: 0 to 1000000.
Supported: 1 to 10000; whole numbers.
Supported: 0 to 1000000.
Supported: 0 to 100000; whole numbers.
Supported: 1 to 100; whole numbers.
Supported: 0 to 99.

Method, formula and assumptions

Full payload = full size x retained full count. Add incremental size x total incremental days, then multiply by total copies. Capacity = copied payload / (1 - reserved fraction).

Input definitions and supported units

  • One full backup (GB): Measured or assumed numerical value, from 0 to 1000000; zero is supported where the stated method permits it.
  • Retained full backups: Whole-number count, from 1 to 10000; must be positive.
  • One incremental day (GB): Measured or assumed numerical value, from 0 to 1000000; zero is supported where the stated method permits it.
  • Total retained incremental days: Whole-number count, from 0 to 100000; zero is supported where the stated method permits it.
  • Total independent copies: Whole-number count, from 1 to 100; must be positive.
  • Capacity reserved for other data (%): Measured or assumed numerical value, from 0 to 99; zero is supported where the stated method permits it.

Worked example with answer

Four 100 GB fulls plus 24 incremental days at 5 GB give 400 + 120 = 520 GB. Two copies need 1,040 GB payload; with 20% capacity reserved, provision 1,300 GB.

How to use the results

The day count is total incremental objects, not days per full. Reserve is a fraction of final capacity, so adding 20% to payload is not the same calculation.

Results retain full precision internally and display up to four decimal places. Very small nonzero results use scientific notation rather than appearing as zero. Check the labels before comparing values across units.

Limitations and references

No deduplication, compression, expiry overlap or restore-chain validation is assumed. Count the actual retained objects from your policy rather than multiplying an ambiguous calendar.

The method is a self-contained arithmetic, geometric or explicitly stated mathematical model. There are no imported tariffs, empirical presets or equipment specifications; measured values and allowances must come from your own process.

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