How much downtime does 99% uptime allow?

99% uptime allows about 7h 12m of downtime per 30-day month, which works out to roughly 3d 16h a year. Go past that in a window and you have missed the target for that window.

What is the error budget for 99% uptime?

Over 5M requests in a month, 99% permits about 50K failed requests before the budget is spent. The budget is 1% of whatever volume you serve, so it scales with traffic.

99% uptime downtime & error budget

99% uptime allows about 7h 12m of downtime per 30-day month, roughly 3d 16h a year. Here is the full ladder, the error budget in requests, and how fast you can burn it.

allowed downtime / month7h 12m30-day window

error budget50K reqsof 5M / month

failure allowance1%of all requests

allowed_downtime

Allowed downtime at 99%, by window

Allowed downtime at 99% across time windows
window	allowed downtime
per day	14m 24s
per week	1h 41m
per 30 days	7h 12m
per 90 days	21h 36m
per 365 days	3d 16h

burn_rate

How fast the monthly budget burns

At 1x you spend the whole 30-day budget exactly over 30 days. 14.4x is Google's fast-burn alert threshold, the rate that drains the month in about two days.

Time to exhaust the 30-day budget at each burn rate
burn rate	budget gone in
1x	30d
2x	15d
5x	6d
10x	3d
14.4x (fast-burn page)	2d 2h

free_toolRun your own volumeThe SLO & Error Budget Calculator, prefilled to 99%. Set your real request volume to size the budget and the burn-rate alerts.free_toolWhat is that downtime worth?The Downtime Cost Calculator puts a dollar figure on this tier and on each extra nine, so you can decide what reliability is worth buying.

what_it_takes

What it takes to hold 99% (two nines)

This is where unmonitored side projects and internal tools sit by default. It needs no redundancy, just a server that mostly stays up. For anything customer-facing it is usually too loose, because a single bad deploy or one long restart can spend the whole month in an afternoon.

Need more? See 99.5% uptime and what the next nine costs.

every_tier

The full uptime ladder

New to the terms? What availability and the nines mean, plus error budgets and burn rate.

faq

Questions & answers

How much downtime does 99% uptime allow?: 99% uptime allows about 7h 12m of downtime per 30-day month, which works out to roughly 3d 16h a year. Go past that in a window and you have missed the target for that window.
What is the error budget for 99% uptime?: Over 5M requests in a month, 99% permits about 50K failed requests before the budget is spent. The budget is 1% of whatever volume you serve, so it scales with traffic.
Is 99% uptime good enough?: It depends on what your users need and what the next tier costs to hold. This is where unmonitored side projects and internal tools sit by default. The breakdown below shows what it takes to hold 99% and whether the next nine is worth it.

Picking a target is easy. Holding it in production is the work.

I review where a system actually spends its error budget and what the next nine really costs. Book a call, or leave your email and I'll reach out.

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