Uptime & SLA Calculator
Calculate allowed downtime for an SLA uptime percentage (99.9%, 99.99%, five nines) across day, week, month, quarter and year — or the reverse: the SLA % a downtime target requires, plus your remaining error budget.
Input
Output
| Period | Allowed downtime | % of period |
|---|---|---|
| No data yet | ||
| SLA tier | Per year | Per quarter | Per month | Per week | Per day |
|---|---|---|---|---|---|
| No data yet | |||||
More ways to use this tool
REST API
curl -X POST https://api.iotools.cloud/v1/tool/uptime-sla-calculator \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"mode": "downtime",
"slaPreset": "99.9"
}'Swap in your own key from your account. The tool's fields are the body — no wrapper.
Ask an AI agent
Use the IOTools `uptime-sla-calculator` tool (Uptime & SLA Calculator) on this input:
YOUR_INPUT_HEREPaste this at any agent connected to the IOTools MCP server, then add your input.
Embed widget
<iframe
src="https://iotools.cloud/embed/uptime-sla-calculator/"
width="100%" height="520" frameborder="0" scrolling="no" loading="lazy"
title="Uptime & SLA Calculator — iotools.cloud"
sandbox="allow-scripts allow-forms allow-same-origin allow-downloads allow-popups allow-popups-to-escape-sandbox"
allow="clipboard-write"
style="width:100%;border:1px solid #e5e7eb;border-radius:12px;overflow:hidden"></iframe>
<script src="https://iotools.cloud/embed.js" async></script>Drop this into your own page — free, no key required, just a link back.
| Cost per API/MCP call | From 5 credits |
|---|---|
| Need more credits? | View pricing |
Also available with
Guides
Turn an SLA uptime percentage into the downtime it actually allows — and back again. Enter a target like 99.9% or 99.999% ("five nines") and see exactly how much downtime you're permitted per day, week, month, quarter and year. Or work in reverse: give it a downtime budget and it tells you the SLA percentage you'd have to hit. Everything runs in your browser, instantly, with nothing sent to a server.
Three modes
- Allowed downtime for an SLA % — pick a common tier (or type a custom percentage) and get a full breakdown by period, plus a side-by-side comparison of every standard SLA tier.
- Required SLA % for a downtime target — say "at most 5 minutes of downtime per month" and it returns the uptime percentage that implies (and the nearest common tier).
- Error budget remaining — enter your SLA and how much downtime you've already burned this period; it shows how much of your error budget is left before you breach.
How the math works
Allowed downtime is simply (1 − uptime%) × period length. At 99.9% uptime the "unavailable" fraction is 0.1%, so over a 365.25‑day year that's 0.001 × 31,557,600 s ≈ 8h 46m. The reverse mode inverts it: uptime% = (1 − downtime ÷ period) × 100.
Two length conventions matter, and this tool uses the same ones as uptime.is and most SRE references:
- Year = 365.25 days (a Julian year), so a quarter is 91.31 days.
- Month = 30 days (the standard flat SLA assumption), week = 7 days, day = 24 hours.
If your contract defines the month or year differently, scale the result accordingly.
Common SLA tiers and their allowed downtime
| SLA uptime | Per year | Per month | Per day |
|---|---|---|---|
| 99% (two nines) | 3d 15h 39m | 7h 12m | 14m 24s |
| 99.5% | 1d 19h 49m | 3h 36m | 7m 12s |
| 99.9% (three nines) | 8h 45m 58s | 43m 12s | 1m 26s |
| 99.95% | 4h 22m 59s | 21m 36s | 43s |
| 99.99% (four nines) | 52m 36s | 4m 19s | 9s |
| 99.999% (five nines) | 5m 16s | 26s | 864ms |
Each extra nine cuts your downtime budget by roughly 10×, which is why the jump from 99.9% to 99.99% — and again to 99.999% — gets expensive fast in engineering and redundancy terms.
What is an error budget?
An error budget is the flip side of an SLA: the total downtime you're allowed to spend in a period without breaking your commitment. A 99.9% monthly SLA gives you 43m 12s of budget; the budget mode tracks how much you've used and how much remains, so you can decide whether it's safe to ship a risky change or ship at all.
Is my data private?
Yes. All calculations happen locally in your browser — no percentages, downtime figures or budgets are uploaded anywhere.