Measure how much of your reserved instances capacity was actually used during a consistent billing period. Enter purchased or available capacity, consumed capacity, unit cost, and the number of comparable periods per year. The calculator reports utilization, unused capacity, current-period unused cost, and an annualized estimate while clearly identifying usage above the entered capacity.
Utilization compares consumed capacity with the capacity you made available. Unused-cost outputs quantify paid headroom but do not decide how much reliability buffer you should retain.
Aiming for exactly 100% may be inappropriate when failover capacity, burst headroom, or interruption risk matters.
With 100 capacity units available, 72 used, and $0.10 per unit, utilization is 72.00%, unused capacity is 28 units, and unused cost is $2.80 for the period.
Yes. That means usage exceeded the entered purchased or available capacity; investigate uncovered usage or oversubscription.
Either works if both values use the same unit and cover the same period.
Unused capacity is multiplied by the entered cost per capacity unit.
No. Very little headroom can increase operational risk, so interpret utilization alongside reliability requirements.
It annualizes the current period’s unused-cost estimate without assuming that the period is always monthly.
| Variable | Meaning |
|---|---|
| Available capacity | Purchased or planned capacity in one consistent unit |
| Used capacity | Capacity actually consumed in the same unit and period |
| Unit cost | Cost for one capacity unit in that period |
| Periods per year | Multiplier used only for annualization |