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Estimate software system latency, throughput, capacity, and cloud costs from first principles using Sirupsen's napkin-math numbers. Use for back-of-the-envelope performance, storage, network, logging, compression, and cost calculations.
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| name | napkin-math |
| description | Estimate software system latency, throughput, capacity, and cloud costs from first principles using Sirupsen's napkin-math numbers. Use for back-of-the-envelope performance, storage, network, logging, compression, and cost calculations. |
| disable-model-invocation | true |
Use this skill to answer quick systems sizing questions: latency budgets, throughput ceilings, storage growth, logging cost, network transfer time, compression tradeoffs, and rough cloud spend.
Treat the bundled numbers as a fallback, not truth forever. The upstream source is https://github.com/sirupsen/napkin-math and can change as hardware/cloud measurements change.
Before doing a calculation that depends on reference numbers:
python3 scripts/napkin_math.py --query '<term>' from this skill directory when looking for specific rows.python3 scripts/napkin_math.py --section all when needing the full compact reference.references/current-numbers.md.Cache behavior:
~/.cache/napkin-math/README.md by default.86400 seconds by default.NAPKIN_MATH_CACHE_DIR and NAPKIN_MATH_TTL_SECONDS.--refresh; skip network with --offline.Never rely on mental arithmetic for final numbers. Use code for every multiplication, division, exponent, unit conversion, and range endpoint.
scripts/napkin_math.py.scripts/calc.py or an explicit Python snippet; include the command or formula in the answer.python3 scripts/napkin_math.py --query memory
python3 scripts/napkin_math.py --query 'blob storage'
python3 scripts/napkin_math.py --section cost
python3 scripts/napkin_math.py --section compression --offline
python3 scripts/napkin_math.py --refresh --section all
python3 scripts/calc.py '100_000/s * 1*KiB * 30*day' --to TiB
python3 scripts/calc.py '80*ms + 1*GiB / (100*MiB/s)' --to s
references/current-numbers.md: bundled compact snapshot and fallback.scripts/napkin_math.py: cache refresh, fallback, section extraction, query filtering.scripts/calc.py: safe arithmetic and unit conversion helper.scripts/test_napkin_math.py: reference script unit tests.scripts/test_calc.py: calculator unit tests.