From calendar days to operating hours
A month is not always 30 days, and a workweek is not the same as a 24/7 schedule. This calculator counts the selected dates first, then applies your daily hours and availability. Both the start and end date are included. Weekdays means Monday to Friday; public holidays are not removed.
The calculation
Scheduled hours = selected operating days × hours per day. Expected runtime = scheduled hours × availability ÷ 100. Expected downtime is the difference between those two figures. Availability applies only inside the chosen schedule: an eight-hour working day does not have sixteen hours of downtime.
Example: an always-on server
For September 1–30, a server scheduled for 24 hours each day has 720 scheduled hours. At 98% availability, expected runtime is 705.6 hours and expected downtime is 14.4 hours. These are planning averages, not a record of actual outages.
Choose an availability figure you can explain
Use monitoring records when you have them. Divide recorded operating hours by scheduled hours and multiply by 100. If you have no history, compare 100%, 98% and 95% instead of treating one guess as a measured fact. Planned maintenance should be included once: either reduce the schedule or account for it in availability.
Use runtime to budget electricity
Runtime is the time component of an energy calculation. Multiply operating hours by measured power in kilowatts to estimate kWh. This works for servers, rendering workstations and ASIC miners as well as ordinary appliances. Equipment that stays powered during a service outage still consumes electricity, so service availability and electrical runtime can be different.
Dates and daylight saving time
This tool counts calendar dates and uses the daily hours you enter. It does not subtract or add a daylight-saving hour and it does not model time zones. For an exact elapsed-time audit, use timestamped equipment logs. For budget planning, the explicit daily schedule is usually the more useful starting point.
Questions about this calculation
Does the end date count?
Yes. Selecting the same start and end date counts as one calendar day.
Are holidays excluded?
No. Weekdays excludes Saturday and Sunday only. Adjust the selected period or daily hours for local holidays.
Is uptime the same as runtime?
Not always. A server may be powered on while its service is unavailable. Use electrical runtime for electricity and service uptime for delivered work.
Method and references
The calculations use the formulas shown above. Energy units and measurement principles can be checked against Australian Government guidance on energy ratings and running costs.
Published September 11, 2026. No live tariff, exchange-rate or revenue feed is used.