Calculator inputs
Example data table
| Scenario | Instances | Hours/Month | Term | Utilization | On-Demand Rate | Reserved Rate | Upfront |
|---|---|---|---|---|---|---|---|
| Steady production | 6 | 730 | 12 months | 92% | $0.2160 | $0.1340 | $650 |
| Mixed workload | 4 | 540 | 12 months | 68% | $0.1920 | $0.1190 | $400 |
| Seasonal burst | 3 | 400 | 6 months | 48% | $0.2550 | $0.1550 | $350 |
Formula used
- Planned hours per month = instances × hours per month × monthly growth factor.
- Actual billed workload = planned hours × utilization rate.
- On-demand total = sum of actual hours × on-demand rate across all months.
- Reserved total = upfront payment + monthly commitment × term + sum of actual hours × reserved rate.
- Savings = on-demand total − reserved total.
- Break-even hours = reserved fixed commitment ÷ (on-demand rate − reserved rate).
- Break-even utilization = break-even hours ÷ total planned reserved hours × 100.
- Estimated waste cost = unused reserved hours × (reserved rate + allocated fixed cost per planned hour).
This model assumes reserved capacity is sized for the planned workload, while actual billed usage depends on utilization. That exposes underused reservations and highlights when flexible pricing remains safer.
How to use this calculator
- Enter the number of instances you expect to run.
- Add the average planned hours per month for each instance.
- Choose the comparison term in months.
- Set the utilization rate to reflect how much reserved capacity will actually be consumed.
- Apply any expected monthly workload growth for scaling plans.
- Enter the on-demand hourly rate from your provider quote.
- Enter the reserved hourly rate, upfront payment, and monthly commitment.
- Click Compare costs to see totals, savings, waste exposure, and break-even thresholds.
- Use the CSV or PDF buttons after calculation to export your results.
Frequently asked questions
1. What does this calculator compare?
It compares total spending for reserved and on-demand cloud pricing over a chosen term. It also estimates break-even utilization, effective hourly cost, savings, and unused reserved capacity waste.
2. Why is utilization important?
Reserved pricing usually wins when capacity stays busy. If utilization falls, fixed commitments spread across fewer consumed hours, pushing the effective reserved cost upward.
3. What is monthly workload growth?
It adjusts planned capacity month by month. Positive growth models expansion, while negative growth reflects shrinking workloads or rightsizing during the reservation term.
4. Does the calculator include partial usage waste?
Yes. It estimates unused reserved hours and assigns them a cost using reserved hourly pricing plus a share of fixed commitments, showing underutilization risk.
5. When should on-demand pricing be preferred?
On-demand is usually safer for short projects, uncertain traffic, seasonal demand, or frequent architecture changes where long commitments may create avoidable waste.
6. What does break-even utilization mean?
It is the workload level required for reserved pricing to offset its fixed costs. Below that point, flexible on-demand pricing may remain cheaper overall.
7. Can I use this for different instance families?
Yes. Enter the pricing and workload assumptions for any instance family, database node, or other metered resource with reserved and on-demand options.
8. Are taxes and support fees included?
Not by default. Add them into the hourly rates or fixed commitments before running the comparison if you want a fully loaded estimate.