Backup Storage Calculator: How Much Backup Storage Do You Need?
The most common mistake in backup planning is sizing storage from the size of the protected data alone. The real requirement can grow several times over depending on the daily change rate, how many restore points you keep, the backup method and the number of copies. This backup storage calculator brings those variables together on one screen to answer how much backup storage you need; the formula is laid out below, so the result is a checkable estimate.
The calculator also scores how well your setup follows the 3-2-1-1-0 rule, out of 5. All calculations run in your browser; nothing you enter is sent to a server.
Turn the Calculated Capacity Into a Safe Backup Design
Storage capacity is only one part of a backup plan. The MAV Cloud team can work through retention policy, number of copies and the need for an immutable copy alongside the calculated figure.
How is backup storage calculated?
Backup storage is the size of a full backup plus the incremental backups you retain, multiplied by the number of copies. The calculator subtracts compression and deduplication savings at each step and adds free-space headroom at the end.
- Full backup: protected data × (1 − saving).
- Daily incremental: protected data × daily change rate × (1 − saving).
- Forever incremental: 1 full + (restore points − 1) incrementals.
- Weekly full + daily incrementals: (restore points ÷ 7, rounded up) + 1 fulls, plus as many incrementals as restore points. The extra chain is counted because the old chain cannot be deleted until the new one is complete.
- Headroom and copies: 10% free-space headroom is added (an assumption), and the result is multiplied by the total number of backup copies.
The defaults are 2,000 GB of protected data, 5% daily change, 30 restore points, 40% saving and 2 copies. The saving rate is an assumption; it typically ranges from 20% to 60% depending on data type and is one of the inputs that moves the result most.
Worked example: how much storage for 2 TB of data?
With 2,000 GB of data, 5% daily change, 30 restore points, 40% saving and 2 copies, forever incremental needs about 6.5 TB and weekly fulls need about 19.8 TB. In both cases a full backup comes to 1,200 GB and a daily incremental to 60 GB.
| Item | Forever incremental | Weekly full + daily incremental |
|---|---|---|
| Full backups | 1 × 1,200 GB | 6 × 1,200 GB |
| Incremental backups | 29 × 60 GB | 30 × 60 GB |
| One copy (incl. 10% headroom) | ≈ 3,234 GB | ≈ 9,900 GB |
| Total (2 copies) | ≈ 6.5 TB | ≈ 19.8 TB |
Weekly fulls use roughly three times the storage here, because a new 1,200 GB full is written every week and six of them sit on disk at once within a 30-day window. In return, this method produces independent chains: corruption in one chain affects only that week. Restores need to combine fewer incremental files, and on storage systems that deduplicate, repeated fulls can cost much less than the table suggests.
What is the daily change rate and how do you measure it?
The daily change rate is the share of protected data that changes or is newly written in a day. Because it sets the size of every incremental, it should be measured rather than guessed.
The best source is your backup software’s job reports: average a few weeks of incremental sizes before compression. Changed block tracking (CBT) data gives the same view. File servers usually change slowly, while busy databases and log files change much faster; periodic peaks such as month-end closing should be added on top of the average.
Restore points versus GFS retention
Restore points are the daily backups you can roll back to; GFS (grandfather-father-son) adds weekly, monthly and yearly long-term copies on top. The calculator covers the daily points, so GFS copies need to be planned separately.
Each GFS level keeps its own full backup: weekly copies may be kept for weeks, monthly copies for months and yearly copies for years. Each adds roughly one full backup to backup retention storage. How many to keep is a business, audit and regulatory decision, not a technical one.
Forever incremental or periodic full backups?
Forever incremental uses the least space with a single full followed by incrementals; periodic fulls trade more space for independent chains. The choice balances storage budget against restore and resilience expectations.
Veeam’s documentation describes how, in a forever forward incremental chain, the oldest incremental restore point beyond retention is merged into the full backup so the chain stays at a fixed length (Veeam Help Center, Backup Methods). Periodic fulls need no merge, which is why they are often preferred on some object and tape storage types.
How much do compression and deduplication save?
Savings depend on the data type and cannot be reduced to one number. The calculator’s 40% is an average starting assumption.
Virtual machines with similar operating system files benefit clearly from deduplication. Databases usually compress well, but the gain drops if the database’s own compression or encryption is enabled. Video, images, archives and encrypted data are already compressed, so savings there should be treated as close to zero. In mixed environments, enter the real ratio from your first full backup report.
An Immutable Copy Against Ransomware
Backups are a target too. Immutable storage prevents backups from being deleted or encrypted before the set retention period ends.
What do the 3-2-1 and 3-2-1-1-0 rules measure?
The 3-2-1 rule calls for at least three copies of data, on two different media types, with one copy offsite. The 3-2-1-1-0 rule adds one immutable or offline copy and zero errors in restore testing.
CISA’s data backup options paper recommends the same approach: three copies made up of one primary and two backups, two different media types and one offsite copy (CISA, Data Backup Options). The calculator derives its 3-2-1-1-0 score out of 5 from the total number of copies and four checkboxes. More detail is in our 3-2-1 backup rule guide.
The value of an immutable copy shows in a ransomware scenario. Once attackers gain administrator rights, deleting or encrypting backups is one of their first moves; a write-locked copy does not allow it. The immutable copy adds a separate copy to the calculated capacity,, and it cannot be cleared during the lock period.
Why is restore testing part of the score?
An untested backup is a file that has not been proven restorable. The zero in 3-2-1-1-0 means no errors in regular restore tests.
Tests should confirm the application starts and the restore finishes within the target time, not just that files are readable. For critical systems, test frequency should follow the data loss and downtime the business can accept.
Retention periods and KVKK
Backups contain personal data too, and retention and destruction obligations under Türkiye’s personal data protection law (KVKK) extend to them. The longer the retention, the more storage you need and the greater the risk that data due for deletion lingers in backups.
When planning long-term GFS copies, check alignment with your personal data retention and destruction policy and document how deletion from backups will work. This section is general information and does not replace legal advice; ask your legal team about periods specific to your organization.
Common sizing mistakes
- Forgetting the number of copies: capacity calculated for one copy doubles or triples once offsite and immutable copies are added.
- Entering an optimistic saving rate: compression gains almost nothing on media and encrypted data.
- Ignoring periodic peaks: month-end, year-end and bulk data loads multiply the daily change for a while.
- Leaving out data growth: a calculation based on today’s data size soon falls short without annual growth added.
- Not planning GFS copies separately: monthly and yearly fulls sit on top of the daily chain.
Backup at MAV Cloud: infrastructure and assurance
MAV Cloud’s cloud backup service is Veeam-based, and backups are stored on infrastructure located in Türkiye. For an immutable copy, a separate immutable backup storage service is available.
The service level agreement sets a monthly availability target of 99.9% for backup services. First-response targets are 15 minutes for critical, 1 hour for high, 4 hours for medium and 1 business day for low priority.
MAV Cloud is certified to ISO/IEC 27001, ISO/IEC 27701, ISO 22301, ISO/IEC 20000 and ISO 9001 (see our certifications).
Frequently Asked Questions
How much backup storage do I need?
There is no single ratio; daily change, restore points, method and number of copies decide it. In the example of 2 TB of data, 5% change, 30 points and 2 copies, forever incremental needs about 6.5 TB.
How accurate is the calculator?
It is a planning estimate. Entering the real saving and change rates from your first backup reports sharpens it considerably.
Are GFS copies included?
No. The calculator covers daily restore points; weekly, monthly and yearly long-term copies should be added separately at roughly one full backup each.
Is anything I enter stored?
No. The calculation runs in your browser and your values are not sent to a server.
Free Review of Your Current Backup Setup
Share your protected data, retention policy and copy layout, and the real storage requirement and any 3-2-1-1-0 gaps can be worked out together.
If your retention policy is still open, use the calculator to compare scenarios; if it is clear, the quote link is the fastest route.