What is an on-demand instance?

An on-demand instance is billed at a fixed hourly rate with no commitment. You pay only for the hours you use and can stop at any time without penalty. It is the most flexible but most expensive pricing option.

What is a reserved instance?

A reserved instance is a billing discount applied to on-demand usage when you commit to a specific instance type and region for 1 or 3 years. The discount ranges from roughly 30% to 72% depending on the term and payment option (no-upfront, partial-upfront, or all-upfront).

How is the break-even point calculated?

The break-even point is the month where cumulative reserved costs (upfront fee plus recurring hourly charges) first become lower than cumulative on-demand costs. Before that month the on-demand option is cheaper; after it the reserved option wins.

What if I have zero upfront cost?

Leave the upfront cost field at 0. The break-even month will be month 1 because the reserved option is cheaper from the first hour. The tool still shows cumulative savings over the projection period.

Does this account for partial utilization?

The calculator assumes the instance runs at the specified hours per day every day. Adjust the daily usage hours field to model partial utilization — for example, a dev instance that runs only 8 hours per day.

Which cloud providers use this model?

AWS (Reserved Instances / Savings Plans), Google Cloud (Committed Use Discounts), Azure (Reserved VM Instances), and Oracle Cloud all offer commitment-based discounts that follow the same break-even math this tool computes.

Reserved vs On-Demand Cloud Cost Comparison

Enter on-demand and reserved hourly rates to see break-even point, total savings, and a cost comparison chart over time.

Pricing Inputs

On-demand hourly rate ($)

Example: $0.192/hr for m5.xlarge on AWS us-east-1

Reserved upfront cost ($)

One-time payment at start of term (0 for no-upfront plans)

Reserved effective hourly rate ($)

Recurring hourly rate after the upfront payment

Daily usage (hours/day)

Reservation term

Projection period (months)

Number of instances

Month-by-Month Breakdown

Month	On-Demand	Reserved	Saved

Fill in the rates above and click Calculate Savings to see the break-even chart and monthly table.

Summary

Cloud providers like AWS, Azure, and GCP offer reserved instances at a significant discount over on-demand pricing in exchange for a 1-year or 3-year commitment. This calculator compares total spend under each model over any time horizon, identifies the exact month you break even on the upfront cost, and shows total savings as a percentage. Use it before committing to a reservation to make sure the workload runs long enough to justify the commitment.

How it works

Enter the on-demand hourly rate for the instance type you are evaluating.
Enter the effective hourly rate for the reserved instance (or enter the upfront cost plus the discounted hourly rate).
Select the reservation term (1-year or 3-year) and how many months you want to project.
The calculator computes cumulative costs for both options month by month.
The break-even month is where the reserved total crosses below the on-demand total.
Savings percentage and total dollar savings are shown for the full projection period.

Use cases

Deciding whether to purchase EC2 reserved instances before a contract renewal.
Evaluating 1-year vs 3-year commitment savings for a steady-state database server.
Justifying a cloud commitment to finance or management with a clear payback timeline.
Comparing partial-upfront vs no-upfront reserved pricing for the same instance.
Stress-testing the reservation decision — what happens if the workload ends early?
Estimating annual cloud infrastructure budget under both pricing models.

Frequently Asked Questions

Last updated: 2026-06-19 · Reviewed by Nham Vu