Calculate savings from using spot or preemptible instances. Factor in interruption rates to estimate real-world cost benefits.
Spot instances (AWS), preemptible VMs (GCP), and spot VMs (Azure) offer massive discounts of up to 90% compared to on-demand pricing. The catch is that the cloud provider can reclaim these instances at any time, typically with a 2-minute warning.
This calculator helps you estimate actual savings from spot pricing by factoring in the interruption rate. If your workload gets interrupted 10% of the time and needs to restart, the effective savings are lower than the headline discount suggests. Enter on-demand and spot prices along with expected interruption rates to see realistic cost projections.
Spot instances are ideal for batch processing, CI/CD pipelines, data analysis, rendering, and any workload that's fault-tolerant and can handle interruptions. This calculator helps you quantify the cost benefit so you can make an informed decision.
Understanding this metric in precise terms allows technology leaders to make evidence-based decisions about scaling, architecture, and infrastructure investment priorities for their organizations.
Spot pricing can save 60–90% on compute costs, but the actual savings depend on interruption frequency and the cost of restarting jobs. This calculator provides a realistic savings estimate that accounts for interruptions, helping you decide whether spot instances are worth the operational complexity for your specific workload. Consistent measurement creates a reliable baseline for tracking system health over time and identifying degradation before it impacts users or triggers costly production outages.
Effective Spot Cost = spot_price × hours × (1 + interruption_rate × restart_overhead) On-Demand Cost = on_demand_price × hours Savings = (On-Demand Cost − Effective Spot Cost) × instances
Result: $478.95 saved/month
On-demand: $0.10 × 730 × 10 = $730/month. Spot with 5% interruption overhead: $0.03 × 730 × 1.05 × 10 = $230.00. Monthly savings: $500/month (68% reduction). Even with occasional interruptions, spot instances deliver substantial savings.
Spot instances use spare cloud capacity that would otherwise sit idle. Providers offer this capacity at steep discounts to recover some revenue. When demand for the capacity rises, spot instances are reclaimed. This creates a dynamic marketplace where prices and availability fluctuate based on supply and demand.
The key to using spot instances effectively is building interruption tolerance into your architecture. This means checkpointing long-running jobs, using message queues to track work items, designing for idempotent operations, and leveraging auto-scaling to replace interrupted capacity automatically.
Rather than requesting a single instance type, spot fleets let you specify multiple instance types and availability zones. The fleet automatically selects the most cost-effective and available options, reducing both cost and interruption risk. AWS Spot Fleet, GCP managed instance groups, and Azure spot VM scale sets all support this pattern.
It varies significantly by instance type and region. Some instance types see less than 5% interruption rates while others exceed 20%. AWS publishes interruption frequency data in the Spot Instance Advisor. Diversifying across types keeps effective rates low.
Headline discounts range from 60–90% off on-demand pricing. After accounting for interruptions and restart overhead, real-world savings typically range from 50–80%. The exact savings depend on your workload's ability to handle interruptions.
Batch processing, CI/CD pipelines, data analytics, rendering, machine learning training, testing environments, and any workload that can tolerate interruptions. Stateless web servers behind auto-scaling groups can also use spot effectively.
You receive a 2-minute warning (on AWS) before the instance is terminated. Your application should handle graceful shutdown, checkpoint progress, and re-queue incomplete work. The instance is stopped or terminated depending on your configuration.
Yes, and this is a best practice. Run your minimum required capacity on on-demand or reserved instances, and use spot instances for additional capacity. Auto Scaling groups can manage this mix automatically.
No, spot prices vary by region, Availability Zone, and instance type based on supply and demand. Less popular regions and instance types tend to have lower prices and fewer interruptions.