What’s the difference between SLA and SLO?

An SLA is a formal contract to customers; an SLO is an internal target. You can use this calculator for either as long as you know the uptime percent.

Can I change the month length?

Yes—mentally adjust the monthly minutes if your period is 28, 30, or 31 days. The yearly value assumes 365 days.

Does scheduled maintenance count?

Some SLAs exclude planned maintenance. Check your terms—this tool simply converts uptime to downtime minutes.

How do I get seconds instead of minutes?

Multiply the daily/monthly/yearly minutes by 60 to get seconds for runbook alerts.

How do I handle 99.95% or custom targets?

Enter any percentage. The math works for all targets below 100%.

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Uptime SLA Calculator

See allowed downtime per day, month, and year for a target uptime percentage.

Results

Downtime per day (minutes): 1.44
Downtime per month (minutes): 43.20
Downtime per year (minutes): 525.60

How to use this calculator

Enter your target uptime percentage (e.g., 99.9%).
Review the allowed downtime per day, per 30-day month, and per 365-day year.
Use these budgets to shape paging policies and maintenance windows.

Inputs explained

Target uptime (%): Availability goal expressed as a percentage (SLA/SLO value).

How it works

Downtime fraction = 1 − (uptime ÷ 100).

We multiply by total minutes in a day, a 30-day month, and a 365-day year.

Formula

Downtime = (1 − Uptime) × Minutes in period

When to use it

Sizing incident response expectations for on-call teams.
Comparing SLA commitments vs. internal SLOs.
Planning maintenance windows to stay within error budgets.

Tips & cautions

Translate results into seconds for operational runbooks where precision matters.
Align the month assumption to your billing period if it differs from 30 days.
Pair this with request-level error budgets for a fuller SLO picture.
Uses a simple 30-day month and 365-day year; adjust if your contract specifies otherwise.
Does not distinguish planned vs. unplanned downtime—treat maintenance separately.
Only time-based; request-based error budgets need additional metrics.

Worked examples

99.9% uptime

Per day ≈ 1.44 min
Per month ≈ 43.2 min
Per year ≈ 8.76 hours

99.99% uptime

Per day ≈ 0.144 min
Per month ≈ 4.32 min
Per year ≈ 52.6 min

Deep dive

This uptime SLA calculator turns availability targets like 99.9% into real downtime budgets per day, month, and year. Enter your uptime goal to see how many minutes of downtime you can afford.

Use it to set on-call expectations, plan maintenance windows, and communicate SLAs or SLOs with stakeholders. Adjust the period lengths if your contracts use different billing cycles.

FAQs

What’s the difference between SLA and SLO?: An SLA is a formal contract to customers; an SLO is an internal target. You can use this calculator for either as long as you know the uptime percent.
Can I change the month length?: Yes—mentally adjust the monthly minutes if your period is 28, 30, or 31 days. The yearly value assumes 365 days.
Does scheduled maintenance count?: Some SLAs exclude planned maintenance. Check your terms—this tool simply converts uptime to downtime minutes.
How do I get seconds instead of minutes?: Multiply the daily/monthly/yearly minutes by 60 to get seconds for runbook alerts.
How do I handle 99.95% or custom targets?: Enter any percentage. The math works for all targets below 100%.

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Results use fixed 30-day months and 365-day years; confirm downtime allowances against your specific SLA or SLO contract language.