Database Index Size Calculator
Estimate the size of a database index based on row count, key size, and pointer size. Plan memory requirements to keep indexes in RAM.
How to Use the Index Size Calculator
- Enter number of rows in the table.
- Enter key size in bytes.
- Enter pointer size (default 8 bytes for 64-bit).
- Click Calculate to get index size and RAM recommendation.
Casi d'Uso
- •Planning database server memory requirements.
- •Evaluating index strategy for large tables.
- •Sizing RAM for high-performance database servers.
- •Comparing composite vs single-column index sizes.
Formula
Index size (MB) = Rows × (key size + pointer size) × 1.3 overhead / 1,048,576.
Domande Frequenti
Why keep indexes in RAM?
Indexes in RAM allow O(log N) lookups without disk I/O, making queries orders of magnitude faster.
What is a typical key size?
INT keys are 4 bytes, BIGINT 8 bytes, VARCHAR(255) up to 255 bytes. Smaller keys = smaller, faster indexes.
What is the 1.3x overhead?
B-tree index overhead accounts for page structure, fill factor gaps, and metadata stored alongside keys.