AWS m8i.16xlargevsAWS m8i.8xlarge

m8i.16xlarge pairs 64 vCPUs with 256GB of RAM at $3.3869/hr On-Demand (about $2439/mo at 24×7). m8i.8xlarge pairs 32 vCPUs with 128GB at $1.6934/hr (~$1219/mo). m8i.8xlarge is 50% cheaper per hour than m8i.16xlarge ($1.6934/hr gap).

Because both instances are in the **m8i family**, the only thing that changes between them is sizing — same silicon, same architecture (Intel Xeon (x86_64)), same burstable/sustained behavior. The choice is purely about how much capacity you actually need: m8i.16xlarge gives you 64 vCPUs and 256GB of RAM, m8i.8xlarge gives you 32 vCPUs and 128GB. AWS scales pricing close to linearly within a family, so picking the right size is mostly about right-sizing your workload, not getting a better deal per vCPU.

On raw price-per-performance, the two are m8i.8xlarge delivers ~101% more single-thread Sysbench score per dollar (977 vs 1963 points per $1/hr). That's the cleanest signal we have for "which one runs your workload faster per dollar," but it only matters if your workload is single-thread-bound; for parallel workloads the multi-core scores (112060 vs 56016) are what to weigh. Spot pricing flips many of these comparisons — when m8i.16xlarge drops to $0.9618/hr and m8i.8xlarge drops to $0.6760/hr, the cheap-per-hour winner can swing meaningfully.

In practice, pick m8i.16xlarge when your workload is closer to general-purpose (balanced general-purpose workloads with a 1:4 vCPU-to-memory ratio). Pick m8i.8xlarge when it's closer to general-purpose (balanced general-purpose workloads with a 1:4 vCPU-to-memory ratio). When neither side is obviously right, the cheaper hourly rate usually wins for fault-tolerant batch workloads, while the higher single-core score usually wins for latency-sensitive web traffic. The regional pricing tables linked from each instance page below show where each is currently cheapest — sometimes a >20% regional gap flips the comparison entirely.