How accurate is the estimate?

The estimate is a close approximation. Actual storage varies by database engine (MySQL InnoDB, PostgreSQL, SQLite, etc.) due to internal page sizes, fill factors, compression, and MVCC overhead. Use this tool for planning and ballpark figures.

Why is an overhead multiplier applied?

Every database engine adds metadata per row (null bitmaps, transaction IDs, row headers) and aligns data to byte or word boundaries. The 1.3x overhead factor accounts for these typical real-world additions.

What does the index overhead option include?

Indexes duplicate column data into separate B-tree structures. Enabling index overhead adds an extra 30% on top of raw table size, which is a rough estimate for one or two secondary indexes.

How should I size VARCHAR columns?

Use the expected average length in characters, not the maximum. For example, a VARCHAR(255) email column with typical 25-character emails should be entered as 25, not 255.

Does this account for compression?

No. Many databases support page-level or row-level compression. If your engine uses compression, actual storage can be 30–70% smaller than the estimate shown here.

Table Storage Estimator

Name: Table Storage Estimator
Availability: InStock
Author: Nham Vu

Enter your row count and column definitions to estimate how much disk space your database table will occupy.

Row Count

Expected number of rows

Columns

Data Type

Avg Size (bytes)

Count

For VARCHAR/TEXT/BLOB, enter the average byte length, not the max.

Options

Apply row overhead (1.3x — null bitmap, alignment, row header) Include index overhead (+30% for secondary indexes)

Define your columns and click
Estimate Storage to see results.

Summary

Enter your row count and column definitions to estimate how much disk space your database table will occupy.

How it works

Enter the expected number of rows in your table.
Add each column by selecting its data type and providing a size for variable-length types.
The estimator calculates bytes per row based on fixed and variable type sizes.
Overhead factors for row headers, alignment padding, and index storage are applied automatically.
Results are shown in bytes, KB, MB, and GB for easy capacity planning.

Use cases

Plan storage capacity before creating a new database table.
Estimate how large a table will grow over time given projected row growth.
Compare storage costs across different schema designs.
Justify infrastructure upgrades with concrete storage projections.
Assess the impact of adding columns to an existing high-volume table.
Estimate backup storage requirements for database tables.

Frequently Asked Questions

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Last updated: 2026-05-23 · Reviewed by Nham Vu