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Memory Requirement Calculator

Work out memory requirement instantly with clear inputs, formula shown and shareable results.

About Memory Requirement Calculator

Memory need is a fixed base plus a per-request allocation multiplied by concurrency, and headroom matters more than the arithmetic suggests: garbage-collected runtimes need spare space to avoid constant collection, and a container without headroom is killed by the OOM killer rather than merely slowing down. Cloud instance memory comes in powers of two, so the answer rounds up.

Formula

Memory sizing

working set = base memory + concurrency x per-request memory; required = working set x (1 + headroom); round up to the next instance size

Worked example

With the default values below, Memory Requirement Calculator returns Memory required of 7.26. Change any input above and every figure here is recalculated in your browser.

Inputs used

Concurrent requestsminimum 1
200
Memory per requestminimum 0.01 MB
24 MB
Base process memoryminimum 1 MB
512 MB
Headroom for garbage collection and spikesaccepts 0–200 %
40 %

Results

Memory required
7.26 GB
Working set without headroom
5,312 MB
Next instance size up
8 GB
Headroom allowance
2,125 MB

Step by step

  1. 1Values used
  2. 2Memory sizing
  3. 3Memory required= 7.26 GB
  4. 4Working set without headroom= 5,312 MB
  5. 5Next instance size up= 8 GB
  6. 6Headroom allowance= 2,125 MB

Assumptions and limits

  • The result is derived only from the 4 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 2 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 much headroom does a JVM need?

Typically 25 to 50 percent above the live set. Below that, collection frequency rises sharply and pause times become the dominant latency source.

What happens if a container exceeds its memory limit?

The kernel kills it immediately with no graceful shutdown. Unlike CPU, memory limits are not throttled — they are enforced by termination.

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