Almost every problem with a cloud commitment portfolio shows up in just two metrics. Commitment coverage tells you how much of your usage is on a discounted rate. Commitment utilization tells you how much of what you bought is actually being used. Read them together and you know whether your discounts are working.
Commitment coverage and utilization are the two numbers that decide whether a reserved instance, savings plan, or committed use discount is saving you money or quietly costing you money. Coverage measures the share of eligible usage that a commitment is discounting; utilization measures the share of a commitment that usage is actually consuming. They pull in opposite directions, and the art of commitment management is holding both high at the same time. This guide explains what each one means, how to calculate it, where the targets sit, and how to read the two together.
This article is part of the complete guide to cloud commitment management. Across the 500-plus environments we have optimized since 2019, the single fastest way to judge the health of a commitment portfolio is to look at these two numbers first; everything else is detail.
Coverage is the percentage of your eligible, on-demand-equivalent usage that a commitment is discounting. If you run 100 units of steady compute and 70 of them are covered by reservations or savings plans, your coverage is 70 percent. The remaining 30 units run at full on-demand price. Low coverage is money left on the table: usage that is stable enough to commit but is still paying the undiscounted rate.
The instinct is to chase 100 percent coverage. That is a trap. Covering the variable, spiky top of your usage curve is exactly how utilization collapses, because the moment that usage drops, you are paying for a commitment that nothing is consuming. Coverage should track the stable base of your usage, not the peak. Finding that base is the subject of how to forecast commitment needs, and committing only to it is why we rightsize before we commit.
Utilization is the mirror image: the percentage of what you have committed to that is actually being used. If you bought a savings plan worth $10 per hour of commitment and your eligible usage only draws down $9 of it in a given hour, your utilization is 90 percent and the unused $1 is pure waste, paid for and consumed by nothing. Unused commitment does not roll over; an idle hour is gone. That is why we treat low utilization as one of the hidden costs of idle commitments.
Utilization is the metric that protects you from over-buying. A portfolio at 70 percent coverage and 99 percent utilization is healthy and conservative. A portfolio at 95 percent coverage and 80 percent utilization is over-committed and leaking money, the failure mode described in the risk of over-committing to cloud discounts.
Coverage: how much of your usage is discounted. Utilization: how much of your discount is used. The first measures opportunity, the second measures waste.
The two metrics are in tension. Buy more commitment and coverage rises, but if you buy past the stable base, utilization falls. Buy less and utilization stays near 100 percent, but coverage and therefore total savings stay low. The optimal portfolio sits where coverage is as high as it can go while utilization stays close to the ceiling. In practice that means committing to the floor of usage, leaving the variable top on-demand, and using flexible instruments like savings plans and convertible reservations to keep utilization high as workloads shift. The instrument trade-offs are laid out in reserved instances vs savings plans vs CUDs.
Across our engagements we manage to these benchmarks, and they are a reasonable starting point for any portfolio:
Coverage equals covered usage hours divided by total eligible usage hours, over a period. Utilization equals used commitment divided by purchased commitment, over the same period. AWS exposes both in Cost Explorer under the reservation and savings plans reports; Azure surfaces reservation utilization in Cost Management; Google Cloud reports CUD utilization and coverage in the billing console. Whatever the provider, pull both numbers on the same cadence and read them as a pair, never alone. A single number lies; the pair tells the truth.
A commitment audit reads both numbers across every account and cloud, finds the idle commitment and the uncovered base, and gives you a buy and adjust plan. On the performance model, if we do not save you money, there is no fee.
Get a commitment audit →The pair sorts every portfolio into one of four states. High coverage and high utilization means you are well optimized, keep monitoring. Low coverage and high utilization means you are leaving savings on the table, buy more on the stable base. High coverage and low utilization means you are over-committed, stop buying and let commitments expire or exchange them. Low coverage and low utilization means the portfolio is both incomplete and misaligned, usually a sign you committed before rightsizing. Whichever state you are in, the fix routes back to the buying sequence in how to build a commitment purchase strategy, and the ongoing measurement in how to track commitment ROI.
Coverage and utilization are the dashboard of the whole commitment cluster. Read the complete guide to cloud commitment management for the full discipline, and download The Commitment Strategy Playbook: RIs, Savings Plans, CUDs for the coverage and utilization worksheets. When you want the numbers managed for you, see our commitment management service.
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