Powers of Two Table - System Design Primer

You’ll sometimes be asked to do ‘back-of-the-envelope’ estimates in system design interviews. For example, you might need to determine how long it will take to generate 100 image thumbnails from disk or how much memory a data structure will take. The Powers of two table is a handy reference for these calculations.

Powers of Two Reference

Power	Exact Value	Approx Value	Bytes
7	128
8	256
10	1,024	1 thousand	1 KB
16	65,536		64 KB
20	1,048,576	1 million	1 MB
30	1,073,741,824	1 billion	1 GB
32	4,294,967,296		4 GB
40	1,099,511,627,776	1 trillion	1 TB

Usage in System Design

This table helps you quickly estimate:

Memory requirements for data structures
Storage capacity needed for different scales of data
Network bandwidth calculations
Cache sizing decisions

Further Reading

Latency Numbers Every Programmer Should KnowEssential latency benchmarks for different computer operations to help with system design decisions

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Powers of Two Reference
Usage in System Design
Further Reading

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