Calculate backup capacity from total data size, redundancy factor, and compression savings, or solve any missing value in KB, MB, GB, or TB.

Estimate storage for effective full copies after compression.

1 means one copy; 2 means two copies. Fractional values represent an explicitly chosen equivalent amount of data.

Enter 0 for no savings or 25 for 25% less space. This is not a ratio such as 2:1. Use measured savings for your data.

Related Calculators

Backup Capacity Formula

The calculator uses total data size, redundancy factor, and compression savings to calculate backup capacity. All storage values are converted to gigabytes internally, then converted back to the unit you selected.

BC = DS × RF × (1 - CR / 100)
  • BC = backup capacity
  • DS = total data size
  • RF = redundancy factor as a decimal
  • CR = space saved by compression as a percentage (0 means no savings; 25 means 25% less space)

If Backup capacity is selected, the calculator uses the formula above. If another solve mode is selected, it rearranges the same formula:

DS = BC / (RF × (1 - CR / 100))
RF = BC / (DS × (1 - CR / 100))
CR = 100 × (1 - BC / (DS × RF))

The calculator has four functions:

  • Calculate backup capacity: enter data size, redundancy factor, and compression savings.
  • Calculate total data size: enter backup capacity, redundancy factor, and compression savings.
  • Calculate redundancy factor: enter data size, backup capacity, and compression savings.
  • Calculate compression savings: enter data size, redundancy factor, and backup capacity.

Illustrative Backup Planning Values

These are illustrative inputs, not typical measured savings. Compression depends on the data. Retention, incremental changes, metadata, deduplication and free-space headroom need separate assessment.

Input Example value Meaning
Redundancy factor 1.0 One full copy of the data.
Redundancy factor 2.0 Two full copies, such as a primary backup and a secondary backup.
Compression savings 10% to 50% Illustrative space savings; enter 10 to 50. The remaining fraction is 1 – CR / 100.
Unit Calculator conversion
1 KB 0.000001 GB
1 MB 0.001 GB
1 GB 1 GB
1 TB 1,000 GB

Example Calculations

Example 1: Calculate backup capacity

You have 500 GB of data, a redundancy factor of 1.5, and a compression savings of 25%.

BC = 500 × 1.5 × (1 - 25 / 100)
BC = 750 × 0.75 = 562.5 GB

The required backup capacity is 562.5 GB, or 0.5625 TB.

Example 2: Calculate compression savings

You have 2 TB of data, a redundancy factor of 1.2, and 1.8 TB of backup capacity.

CR = 100 × (1 - 1.8 / (2 × 1.2))
CR = 100 × (1 - 0.75) = 25%

The required compression savings are 25%.

FAQ

What does redundancy factor mean?

Redundancy factor represents how many effective copies of the data you need to store. A value of 1 means one full copy. A value of 2 means enough capacity for two full copies. Values between those numbers can represent partial redundancy, retention overhead, or other backup policy requirements.

Why do I need to enter exactly three values?

Select the value to solve for, then enter the three displayed inputs. Data size, capacity and effective copies must be positive. Savings must be at least 0% and less than 100%; 100% would imply storing nonzero data in zero space.

Which storage unit should I use?

You can use KB, MB, GB, or TB. The calculator converts the selected unit to GB for the calculation and then converts the result back to your selected output unit. It uses decimal conversions, where 1 TB equals 1,000 GB.