Uptime SLA Calculator
Convert an SLA uptime percentage into allowed downtime per year, month and day — for any value like 99.97%.
Formula last reviewed 4 August 2026 · How we verify our calculators
Allowed downtime / year
8.76 hrs (525.6 min)
- Per month
- 43.8 min
- Per day
- 1.44 min
Updates live as you type
Frequently asked questions
It is the share of time a service guarantees to be available. The rest is allowed downtime. 99.9% ("three nines") permits about 8.76 hours of downtime per year.
Multiply total time by (1 − uptime%). A year has 525,600 minutes, so 99.9% allows 525,600 × 0.001 = 525.6 minutes (~8.76 hours) of downtime.
Each extra nine cuts downtime roughly tenfold: 99% ≈ 3.65 days/yr, 99.9% ≈ 8.76 hrs, 99.99% ≈ 52.6 min, 99.999% ≈ 5.26 min.
Usually not. SLAs often exclude scheduled maintenance and force majeure, and breaching one typically yields service credits rather than full compensation. Read the specific terms.
A headline percentage that still permits hours of real downtime
"99.9% uptime" sounds reassuring right up until it's converted to actual outage time. At the 99.9% target, this calculator computes 525,600 × (1 − 0.999) = 525.6 minutes a year — that's 8.76 hours, 43.8 minutes a month, or just 1.44 minutes a day. Push the target to 99.99% on the identical service instead, and allowed downtime drops to about 52.6 minutes a year — roughly a tenth of the three-nines figure. That gap is exactly why chasing one extra nine of uptime is such a demanding, expensive engineering commitment: it means designing for outages measured in single minutes across an entire year, not hours.
The general formula behind every value on the nines table
This tool turns any uptime percentage — including odd values like 99.97% that don't sit neatly on the standard nines table — into downtime allowed per year, month and day. The formula is general: downtime = total time × (1 − uptime%). Because a year holds 525,600 minutes, each additional "nine" cuts the allowance roughly tenfold — 99% leaves about 3.65 days a year, 99.9% about 8.76 hours, 99.99% just 52.6 minutes, 99.999% only 5.26 minutes.
Use it to compare provider SLAs on a like-for-like basis, set realistic internal reliability targets, and size your on-call rotation and redundancy investment against the actual downtime budget a given SLA implies. Remember that most SLAs exclude scheduled maintenance windows from the downtime count and typically compensate breaches with service credits rather than a cash refund — so always read the fine print of the specific agreement before treating a percentage as a hard guarantee.