VM Resource Calculator — How Much CPU, RAM and Storage Does Your Workload Need?

Our free VM resource calculator estimates vCPU, RAM and storage requirements for virtual machines based on workload type and expected load. Use this tool when sizing virtual machines on VMware vSphere, Microsoft Hyper-V, AWS EC2, Azure VMs, Google Compute Engine or any other virtualisation platform — before you deploy and find your application crawling under load.

VM Sizing Principles

Right-sizing VMs is one of the most impactful ways to control cloud costs. Oversizing wastes money (cloud providers charge for allocated resources, not just usage). Undersizing causes performance problems that are harder to diagnose than hardware issues. The goal is to start conservatively, monitor actual utilisation for 2–4 weeks, and adjust based on real data.

Cloud Instance Size Comparison

• AWS t3.micro — 2 vCPU, 1 GB RAM — dev/test, very low traffic
• AWS t3.medium — 2 vCPU, 4 GB RAM — small web apps, light databases
• AWS m6i.large — 2 vCPU, 8 GB RAM — general purpose production workloads
• AWS c6i.xlarge — 4 vCPU, 8 GB RAM — compute-intensive (web servers, APIs)
• AWS r6i.xlarge — 4 vCPU, 32 GB RAM — memory-intensive (databases, caches)

Key VM Sizing Rules of Thumb

• Always add 30% headroom above peak expected load
• For databases, RAM matters more than CPU — the more of your working set that fits in memory, the fewer disk reads are needed
• For web/app servers, CPU and network bandwidth are the typical bottlenecks
• For Kubernetes worker nodes, leave 10–20% of resources as system reserved for kubelet, container runtime and OS processes
• Monitor with tools like Prometheus + Grafana, CloudWatch or Azure Monitor to right-size after deployment