Computer & IT
Cloud Compute Capacity Calculator
Convert request throughput, CPU demand, concurrency memory, node limits, target utilization, redundancy, and reserve into deployable compute nodes.
Compute fleet sizing
Size cloud nodes from CPU demand, concurrent memory, reserve, and failure redundancy
CPU and memory are evaluated independently; the larger workload constraint sets node count before spare nodes are added.Capacity rack
CPU versus memory gate and provisioned node slots
The constraint rails show fractional demand; the rack distinguishes workload nodes, redundancy, and unused capacity within provisioned nodes.Detailed calculation process
Convert per-request resource work into two independent node constraints
General symbolic formulas
C = λt / (1000u)NCPU = ceil(C / c)G = k m(1+r) / 1024NMEM = ceil(G / g)Nwork = max(NCPU,NMEM)Nfleet = Nwork + NredCPU milliseconds per second become continuously occupied cores. Memory uses concurrent requests rather than throughput because those allocations overlap in time.
Symbols and units
Worked substitution with current inputs
Fleet capacity register
| Resource | Demand | Per node | Workload nodes | Fleet capacity |
|---|
Use steps
- Measure CPU time at representative load.
- Count live concurrent request memory.
- Choose utilization and redundancy from SLOs.
Examples
CPU service: optimization can reduce nodes without changing concurrency.
Memory service: large in-flight payloads can dominate despite low CPU.
Limitations
This steady-state model excludes burst queues, autoscaling delay, cold starts, operating-system overhead beyond usable memory, noisy neighbours, network and disk limits, affinity rules, zones, quotas, and price.
Cloud-compute FAQ
Why divide CPU by target utilization?
It preserves operating headroom instead of sizing at sustained 100% CPU.
Are redundant nodes counted in workload capacity?
They are provisioned spare capacity and should remain available for failure or maintenance.
Should requests per second size memory?
Not directly; overlapping concurrency and per-request resident memory determine this simplified memory demand.