See how many seconds, minutes, or hours you can be offline and still hit your SLA. Also reverse: enter downtime and get the uptime you achieved.
Pick a common SLA target, or enter a custom uptime and period.
You already know how long you were down. What uptime did you achieve?
Formula used
allowed_minutes = days × 24 × 60 × (1 − uptime / 100)
30 × 24 × 60 × (1 − 99.9 / 100) = 43.2
uptime% = 100 × (1 − downtime_minutes / period_minutes)
An SLA (Service Level Agreement) often promises a target like “99.9% uptime.” That number is not magic. It is a budget: how much time the service can be offline and still meet the promise.
Allowed downtime is that budget, written in time (seconds, minutes, or hours). If you stay inside the budget, you meet the uptime target. If you go over, your real uptime drops below the target.
This tool uses one clear formula. It matches the method on our SLA uptime → downtime reference and the same math used in the SLA Penalty Calculator.
Allowed downtime (minutes) = days × 24 × 60 × (1 − uptime / 100)
Achieved uptime (%) = 100 × (1 − downtime_minutes / (days × 24 × 60))
Managers often hear “three nines” or “four nines” and stop there. Engineers need the time budget. Finance needs the money risk. Allowed downtime is the bridge between the percentage and a real plan.
Example A — 99.9% over 30 days
Period = 30 × 24 × 60 = 43,200 minutes.
Allowed = 43,200 × (1 − 0.999) = 43,200 × 0.001 = 43.2 minutes.
That is 2,592 seconds, or 0.72 hours. One longer outage can use the whole month’s budget.
Example B — 99.99% over 30 days
Allowed = 43,200 × 0.0001 = 4.32 minutes (about 259 seconds).
Four nines sounds close to three nines. The budget is about 10× smaller.
Example C — Inverse check
You had 60 minutes of downtime in a 30-day month.
Uptime = 100 × (1 − 60 / 43,200) ≈ 99.861%.
That misses a 99.9% promise (budget was only 43.2 minutes).
Example D — Calendar month length matters
Same 99.9% target in a 31-day month: 31 × 24 × 60 = 44,640 minutes.
Allowed = 44,640 × 0.001 = 44.64 minutes — a bit more than the 30-day figure.
Always match the period your contract uses.
Example E — February (28 days) at 99.9%
Period = 28 × 24 × 60 = 40,320 minutes.
Allowed = 40,320 × 0.001 = 40.32 minutes.
That is almost three minutes less than a 30-day model. If your vendor uses calendar months, do not copy a “30-day blog number” into a February credit claim.
Example F — Several short outages add up
You had four incidents of 12 minutes each in a 30-day month → 48 minutes total.
Against a 99.9% budget of 43.2 minutes, you are over by 4.8 minutes.
Achieved uptime = 100 × (1 − 48 / 43,200) ≈ 99.889%. Many teams only remember the “big” outage and forget the small ones. Sum them first, then use the inverse calculator.
Example G — 99.95% over a week
Period = 7 × 24 × 60 = 10,080 minutes.
Allowed = 10,080 × (1 − 0.9995) = 10,080 × 0.0005 = 5.04 minutes.
Weekly budgets are tight. A single bad deploy on Monday can spend the whole week’s allowance. Use weekly views for error budgets; use monthly views when the contract is monthly.
Example H — Year view for planning
99.9% over 365 days: 365 × 24 × 60 = 525,600 minutes.
Allowed = 525,600 × 0.001 = 525.6 minutes (~8.76 hours).
Year numbers help finance and capacity planning. Credit claims still follow the period in your contract (often a calendar month).
Many cloud vendors measure availability over the real calendar month (28, 29, 30, or 31 days), not a fixed “30-day slab.”
Tip in one line: wrong period length → wrong allowed minutes → weak credit math.
Allowed downtime is only useful if you know how long you were actually down. Weak monitoring creates false comfort.
Allowed downtime answers “how much time can we lose?” It does not answer “how much money do we lose?” or “what credit do we owe?”
For money impact of an outage, use Website Downtime Cost. For contract credits when you miss a target, use SLA Penalty Calculator. To compare the cost of buying a higher “nine,” use Cost of Extra Nines.
Over a standard 30-day month (43,200 minutes):
Full day / week / month / year tables live on the reference guide. This page is the interactive version of that same formula.
These are estimates for planning. Real contracts define “unavailable” in their own words (health checks, region scope, multi-AZ rules, and more). Numbers here do not replace legal review. They help you ask better questions.
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SLA uptime → downtime reference · SLA Penalty Calculator · Cost of Extra Nines · Downtime Cost Calculator