Container Resources Calculator
Total CPU and memory a set of container replicas requests, how many nodes that needs, and what is left over once the system reserves its share.
Each replica requests a share of CPU (measured in millicores, where 1000m is one core) and memory.
How the container resources calculator works
Each replica requests a share of CPU (measured in millicores, where 1000m is one core) and memory. Multiply by the replica count for the workload total. Nodes cannot give all of their capacity to workloads: the operating system, the kubelet and system daemons reserve a portion, typically 10–20%. The node count is then the total request divided by the allocatable remainder, taking whichever of CPU or memory runs out first.
Formula: nodes = ⌈max(total CPU ÷ allocatable CPU, total memory ÷ allocatable memory)⌉
Worked examples
| Inputs | Nodes needed | Note |
|---|---|---|
| 20 replicas of 500m / 512 MB on 8-core nodes | 2 | 10 cores requested → 2 nodes |
| Memory-heavy workload | 3 | memory becomes the limit |
| A single large replica | 2 | 2 nodes |
FAQFrequently asked questions
What is a millicore?
A thousandth of a CPU core. 500m is half a core; 2000m is two cores.
Why can I not use the whole node?
The kubelet, container runtime and operating system reserve capacity — typically 10–20%. Requesting the full node size means pods never schedule.
Should I set requests or limits?
Requests decide scheduling and therefore this calculation. Limits cap usage; setting them equal gives predictable performance at the cost of flexibility.
What if CPU and memory are unbalanced?
The "limited by" row tells you which runs out first. Rebalancing requests, or choosing a node type with a different ratio, saves real money.
Does this include headroom for failures?
No — add at least one node so the cluster survives losing one, the same N+1 logic as server capacity.
Where these figures come from
- IEC 80000-13 — Information science and technology (quantities and units) — the decimal (kB, MB) versus binary (KiB, MiB) prefixes used throughout
- RFC 4632 — Classless Inter-domain Routing (CIDR) — the address-plan arithmetic behind the subnet calculator
- RFC 1918 — Address Allocation for Private Internets — the private ranges the subnet calculator recognises
- NIST SP 800-63B — Digital Identity Guidelines, Authentication — length over composition rules; the basis of the password guidance here
- NIST SP 800-57 Part 1 — Recommendation for Key Management — key-strength comparisons used by the key-space calculator
- Australian Cyber Security Centre — Essential Eight — national guidance on passphrases and system hardening
Last checked: September 2026. Units follow the SI decimal convention (IEC 80000-13 defines the binary alternatives); network and security figures cite the defining standard.