AWS c5.18xlargevsAWS c5.24xlarge

c5.18xlarge pairs 72 vCPUs with 144GB of RAM at $3.0600/hr On-Demand (about $2203/mo at 24×7). c5.24xlarge pairs 96 vCPUs with 192GB at $4.0800/hr (~$2938/mo). c5.18xlarge is 33% cheaper per hour than c5.24xlarge ($1.0200/hr gap).

Because both instances are in the **c5 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: c5.18xlarge gives you 72 vCPUs and 144GB of RAM, c5.24xlarge gives you 96 vCPUs and 192GB. 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 c5.18xlarge delivers ~22% more single-thread Sysbench score per dollar (386 vs 316 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 (64417 vs 90367) are what to weigh. Spot pricing flips many of these comparisons — when c5.18xlarge drops to $0.9178/hr and c5.24xlarge drops to $1.2140/hr, the cheap-per-hour winner can swing meaningfully.

In practice, pick c5.18xlarge when your workload is closer to compute-optimized (CPU-bound work — batch processing, web servers under sustained load, game servers). Pick c5.24xlarge when it's closer to compute-optimized (CPU-bound work — batch processing, web servers under sustained load, game servers). 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.