Time Converter
Convert durations between seconds, minutes, hours, days, weeks, months and years. Useful for billing hours, project estimates, uptime figures and "how long is a million seconds" curiosities.
How to use this calculator
- Enter the duration value.
- Choose the from and to units.
- Press Convert to see it in every unit, seconds through years.
Formula used
Months and years here use calendar averages: a month = 30.44 days and a year = 365.2425 days (the Gregorian mean, which accounts for leap years). For exact date-to-date spans, use the date difference calculator instead.
Example calculation
Convert 90 minutes to hours: 90 × 60 ÷ 3,600 = 1.5 hours. And a million seconds? About 11.57 days — while a billion seconds is 31.7 years.
Time units and their quirks
Time is the one system everyone shares — but it's base-60 (Babylonian heritage) up to hours, base-24 to days, then messy: months vary from 28 to 31 days and years need leap corrections. That's why this converter uses average month and year lengths, matching how rates like "per month" are typically annualized.
Useful anchors: a work year ≈ 2,080 hours, a day = 86,400 seconds, and 10,000 hours (the famous mastery figure) ≈ 417 days of nonstop practice.
Why use this calculator?
- Convert billing units — hours to days, minutes to decimal hours for timesheets.
- Translate uptime and SLA figures (99.9% of a year = 8.77 hours of downtime).
- Average-month and average-year factors handled correctly for rate math.
Frequently asked questions
How many seconds are in a day, a year?
A day has 86,400 seconds (24 × 3,600). An average year has about 31.56 million seconds. A million seconds ≈ 11.6 days; a billion ≈ 31.7 years.
How many working hours in a month?
Around 173 hours on average (2,080 hours ÷ 12), though actual months range from ~160 to ~184 depending on weekdays. Payroll systems typically use the 173.33 average.
Why is a month counted as 30.44 days?
It's the calendar average: 365.2425 days ÷ 12. Using it keeps monthly↔yearly conversions consistent, which matters for interest rates, salaries and subscriptions.