Database Storage Estimate Calculator
Estimate a table’s storage from its row count, average row size and index overhead — data size, index size and total disk footprint.
How it works
Data = rows × avg row bytes · Total = data × (1 + index %) · Projected = total × (1 + growth %)
A rough table footprint is just the number of rows times the average bytes per row, but that undercounts real disk use because indexes, per-row overhead and page fill factor add substantial space on top. Applying an index-overhead percentage captures that, and a growth allowance turns today’s size into a capacity plan. It is an estimate — actual on-disk size varies with the engine, compression, data types and fragmentation — but it is the right first-order figure for provisioning.
Worked example
A table of 1,000,000 rows averaging 200 bytes each holds 200,000,000 bytes = 200 MB of data. With 30% index overhead the total is 200 MB × 1.30 = 260 MB. Planning for 50% more rows would push the estimate to 260 MB × 1.50 = 390 MB.
Frequently asked questions
Why include index overhead?
Indexes are separate structures that duplicate key columns to speed lookups, and heavily indexed tables can carry index data that rivals or exceeds the row data. Ignoring them badly underestimates disk use, so a percentage of the data size is a practical allowance.
Will my database use exactly this much disk?
No — treat it as a planning estimate. Real usage depends on the storage engine, page/block size and fill factor, data-type padding, compression, TOAST/overflow storage for large values, and fragmentation. Measure the live table for exact numbers.
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This calculator is for educational purposes. Double-check important results before acting on them.