Database Storage Calculator
Accurate database storage estimation is critical for infrastructure planning, cloud provisioning, and budget forecasting. Under-estimating storage leads to emergency expansions and potential downtime; over-estimating wastes budget. This calculator estimates your current database size based on row count, average row size, and index overhead, then projects storage needs over a multi-year horizon using your expected annual growth rate. It accounts for table data, index overhead, transaction logs, and a free-space buffer. Results are shown in gigabytes (GB) and terabytes (TB) to align with cloud provider pricing units.
Database storage formula
data_GB = rows * row_bytes / (1024^3)
total_GB = data_GB * (1 + index_pct/100 + log_pct/100)
projected_GB = total_GB * (1 + growth_rate/100)^years
provision_GB = projected_GB * 1.25 (25% buffer)
Storage planning best practices
- Add at least 25% free space to your projected size as a buffer for page splits and temporary space.
- Monitor actual growth monthly and compare to projections; adjust forecast models when trends change.
- Consider compression: many databases achieve 2-4x compression on text-heavy tables, reducing storage costs significantly.
- Archive historical data to cheaper cold storage tiers when it is no longer accessed regularly.
- Separate data, index, and log files onto different storage volumes for performance and capacity flexibility.
Frequently asked questions
How do I estimate database storage size?
Multiply the number of rows by the average row size in bytes to get the base table data size. Add index overhead (typically 10-30% of table size), transaction log size (often 10-25% of data size), and free space buffer (15-20%). Then project growth over your planning horizon using your expected growth rate.
How much overhead do database indexes add?
Index storage overhead varies by index type and selectivity. B-tree indexes on high-cardinality columns typically add 10-30% of the indexed column data size. Tables with many indexes can see 50-100% overhead over raw data. PostgreSQL and MySQL report actual index sizes via system catalog queries.
What is the difference between data size and database file size?
The database file (data file) is always larger than the actual data because of page overhead, free space within pages, fill factor settings, and space reserved for future growth. SQL Server pages are 8 KB; MySQL InnoDB pages are 16 KB by default. Effective data density is typically 60-80% of total file size.
How do I calculate storage for BLOB or large object columns?
BLOB, TEXT, and large VARCHAR columns are often stored separately from the main row in overflow pages. Calculate BLOB storage separately: multiply average BLOB size by the number of rows that contain BLOBs. Add this to your regular row size estimate.
How often should I review database storage capacity?
Review storage capacity at least quarterly for growing databases. Set automated alerts at 70% disk utilization for the data volume and at 80% for log files. Monitor growth rate trends monthly and re-forecast annually or when growth rate changes significantly due to new features or increased usage.
Official sources
- NIST: SP 800-111 - Guide to Storage Encryption Technologies for End User Devices.
- IEEE: IEEE Computer Society Publications.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.