Database Row Size Calculator
Estimate row size from column types plus per-row and page overhead.
About Database Row Size Calculator
Databases read whole pages, so rows per page determines how much input and output a scan costs. Narrow rows fit more per page and scan proportionally faster. A row slightly over half a page size wastes nearly half of every page, which is why row width has outsized effects on scan performance.
Formula
Database Row Size
Row size = column data + per-row header; rows per page = usable page bytes ÷ row size
- page
- The fixed block a database reads and writes, commonly 8 KB
- page waste
- Leftover bytes when rows do not divide evenly into a page
Worked example
With the default values below, Database Row Size Calculator returns Row Size of 416. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Integer columnsminimum 0
- 6
- Big integer or timestamp columnsminimum 0
- 4
- Variable text columnsminimum 0
- 8
- Average text lengthminimum 0
- 40
- Per-row header overheadminimum 0 bytes
- 24 bytes
Results
- Row Size
- 416 bytes
- Column Data Size
- 392 bytes
- Rows per 8 KB Page
- 19
- Share That Is Overhead
- 5.769%
- Wasted Bytes per Page
- 264 bytes
Step by step
- 1Values used
- 2Database Row Size
- 3Row Size= 416 bytes
- 4Column Data Size= 392 bytes
- 5Rows per 8 KB Page= 19
- 6Share That Is Overhead= 5.769
- 7Wasted Bytes per Page= 264 bytes
Assumptions and limits
- The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Database Row Size calculated?
Row size = column data + per-row header; rows per page = usable page bytes ÷ row size Databases read whole pages, so rows per page determines how much input and output a scan costs. Narrow rows fit more per page and scan proportionally faster.
Why does Database Row Size matter?
A row slightly over half a page size wastes nearly half of every page, which is why row width has outsized effects on scan performance.
What values do I need to enter?
This calculator takes 5 inputs: Integer columns, Big integer or timestamp columns, Variable text columns, Average text length, Per-row header overhead. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.