Reserved vs On-Demand Calculator
Find the utilisation at which a reservation beats on-demand, including any up-front payment spread across the term.
About Reserved vs On-Demand Calculator
A reservation is a fixed monthly charge for the whole term, so the question is never the headline discount but how many hours you would have bought at on-demand rates instead. Dividing the committed monthly cost by the on-demand hourly rate gives that hour count directly, and expressing it as a share of 730 turns it into a utilisation threshold you can check against your own metrics. Commitments are the largest discount available without renegotiating an agreement, but they are the wrong tool for bursty or seasonal capacity — below the break-even utilisation you pay more than you would have on demand. Rates differ by region, family and agreement, so confirm both sides of the comparison on your provider's pricing page.
Formula
Reserved vs On-Demand
committed monthly = reserved rate × 730 + up-front ÷ term months; break-even hours = committed monthly per instance ÷ on-demand rate; break-even utilisation = break-even hours ÷ 730.
- 730
- Hours a reservation is billed for every month, running or not
- break-even hours
- Hours per month the instance must run before the commitment pays off
- up-front ÷ term
- Any partial or all-upfront payment spread evenly across the commitment
Worked example
With the default values below, Reserved vs On-Demand Calculator returns Monthly Saving from Committing of $301.01. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Instances under considerationaccepts 1–20,000 instances
- 10 instances
- On-demand rateaccepts 0–200 USD/hour
- 0.096 USD/hour
- Committed hourly rateaccepts 0–200 USD/hour
- 0.0403 USD/hour
- Up-front payment per instanceaccepts 0–500,000 USD
- 0 USD
- Commitment termone of 1 year, 3 years, 5 years
- 3 years
- Hours each instance actually runsaccepts 0–744 hours/month
- 620 hours/month
Results
- Monthly Saving from Committing
- $301.01
- Committed Monthly Cost
- $294.19
- On-Demand Monthly Cost
- $595.20
- Break-Even Running Hours
- 306 hours/month
- Break-Even Utilisation
- 42.0%
- Effective Discount Achieved
- 58.0%
- Saving over the Whole Term
- $10,836.36
- Commit or Stay Flexible
- Comfortably ahead of break-even, so the commitment is worth making
Step by step
- 1Values used
- 2Reserved vs On-Demand
- 3Monthly Saving from Committing= 301.01
- 4Committed Monthly Cost= 294.19
- 5On-Demand Monthly Cost= 595.20
- 6Break-Even Running Hours= 306 hours/month
- 7Break-Even Utilisation= 42.0
- 8Effective Discount Achieved= 58.0
Assumptions and limits
- The result is derived only from the 6 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, fees or charges or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Reserved vs On-Demand calculated?
committed monthly = reserved rate × 730 + up-front ÷ term months; break-even hours = committed monthly per instance ÷ on-demand rate; break-even utilisation = break-even hours ÷ 730. A reservation is a fixed monthly charge for the whole term, so the question is never the headline discount but how many hours you would have bought at on-demand rates instead. Dividing the committed monthly cost by the on-demand hourly rate gives that hour count directly, and expressing it as a share of 730 turns it into a utilisation threshold you can check against your own metrics.
Why does Reserved vs On-Demand matter?
Commitments are the largest discount available without renegotiating an agreement, but they are the wrong tool for bursty or seasonal capacity — below the break-even utilisation you pay more than you would have on demand. Rates differ by region, family and agreement, so confirm both sides of the comparison on your provider's pricing page.
What values do I need to enter?
This calculator takes 6 inputs: Instances under consideration, On-demand rate, Committed hourly rate, Up-front payment per instance, Commitment term, Hours each instance actually runs. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.
Does an up-front payment change the break-even point?
Yes. Spreading the up-front across the term raises the effective monthly cost of the commitment, which pushes the break-even hours up. All-upfront usually buys a slightly deeper discount, but it also means the money is gone if the workload disappears in month four.