Convert an uptime percentage into hours of downtime per year, then into lost revenue and productivity.
How it works
Downtime hours per year = (1 − uptime) × 8,760Cost per hour = (annual revenue × dependent share ÷ 8,760) + staff × hourly cost × productivity lostAnnual cost = downtime hours × cost per hour
Defaults are illustrative examples, not benchmarks. Replace them with your own numbers. Prices from our reviews are indicative and dated.
What the nines really mean
Uptime guarantees sound similar but differ a lot in practice. 99% uptime allows about 87.6 hours of downtime a year; 99.9% about 8.8 hours; 99.99% under an hour. Whether the difference matters depends on how much of your revenue and work depends on the system staying up.
Read the SLA small print
- Most hosting SLAs compensate with service credits — a refund on your hosting fee, not your lost sales.
- Planned maintenance is often excluded from the uptime calculation.
- Check how downtime is measured and whether you must claim credits yourself.
Worked example
Take an online store with $500,000 annual revenue, 80% of it dependent on the website, and five staff costing $40 an hour who lose half their productivity during an outage. At 99.9% uptime the site can be down about 8.8 hours a year. Each hour costs roughly $46 in lost sales plus $100 in lost productivity — about $1,300 a year. At 99% uptime the same business would lose about 87.6 hours, or around $12,800.
How to reduce downtime cost
- Choose hosting with redundancy and a clear SLA, and monitor uptime independently.
- Put a CDN in front of your site so cached pages stay available during origin problems.
- Keep tested backups and a documented restore procedure.
- Schedule maintenance for your quietest hours and communicate it in advance.
Using the result
Compare the annual cost of expected downtime with the price difference between hosting or backup options. If an hour of downtime costs more than a year of premium hosting, upgrading is an easy decision. The calculator also helps justify monitoring, backups and support contracts to stakeholders.
- Use real revenue and conversion data where you have it
- Include staff time lost when internal systems are down
- Consider peak periods — downtime during a campaign costs more
Frequently asked questions
Is 99.9% uptime good enough?
For most small-business websites, yes. For online stores with high hourly revenue, the cost difference often justifies better hosting or redundancy.
How do I measure my actual uptime?
Use an uptime monitoring service that checks your site every minute and alerts you. Many have free tiers.
What uptime should I expect from a host?
Many hosts advertise 99.9% or higher; check how they define it and what compensation applies.
How do I reduce downtime?
Choose reliable hosting, use a CDN, keep daily backups with fast restores and monitor uptime.