What this calculates
Enter a length of time in seconds, minutes, hours, days, weeks, months or years, and this shows it in all seven at once, with each conversion worked through. It also places the length on a scale of five bands — seconds, minutes, hours, days and years — so the size of a length of time can be read at a glance.
Months and years are averages, not calendar lengths. It converts a length of time as it is; it does not count between two dates.
The formula
Every conversion goes through seconds: into seconds with one unit's size, then out again with another's.
Into seconds
s = time × seconds in one unitOut of seconds
time = s ÷ seconds in one unitEach unit's size comes from its definition.
Minutes and hours
1 min = 60 s · 1 h = 60 min = 3,600 sDays and weeks
1 d = 24 h = 86,400 s · 1 wk = 7 d = 604,800 sThe average year
1 yr = (400 × 365 + 97) ÷ 400 d = 365.2425 d = 31,556,952 sThe average month
1 mo = 1 yr ÷ 12 = 30.436875 d = 2,629,746 sThe year is the average Gregorian year: 97 of every 400 years are leap years, so a year averages 365.2425 days. The month is a twelfth of that. Every unit is a whole number of seconds, so nothing is rounded on the way; where a seconds figure runs past ten significant figures, the working shows it to ten, marked ≈, while every result is worked out from the exact value.
Worked example
Some conversions come out exact. 1 wk is exactly 168 h, 1 yr is exactly 365.2425 d and 12 mo, and 1 d is exactly 86,400 s.
When to use it, and the mistakes to avoid
Use it when a length of time is given in a unit you do not think in, when turning a count of seconds or minutes into hours or days, and when you want a rough sense of a length in weeks, months or years.
The mistakes that cost the most:
- Reading decimal hours as hours and minutes. 1.5 h is 1 hour and 30 minutes, not 1 hour 50 minutes, because an hour has 60 minutes, not 100. 2.5 h is 150 min.
- Treating every month as 30 days. An average month is 30.43688 d, so 6 mo is 182.6213 d, not 180.
- Treating every year as 365 days. An average year is 365.2425 d, so 10 yr is 3,652.425 d — more than two days past 3,650.
- Using averages for real dates. Months and years here are averages. A real month runs 28 to 31 days and a real year 365 or 366, so a span between two actual dates needs a date calculator, not this converter.
- Expecting every digit of every result. Results are shown to seven significant figures — 1 month shows as 30.43688 d — while each is worked out from the exact value. A length far too small for a unit, such as 0.000000001 s in months or years, reads as 0, and a note under the result says so rather than leaving a silent zero.
- Entering a negative length. This version converts a length of time as it is and does not count back from a date, so it refuses a negative value with a message instead of converting it.
FAQ
How do I convert hours to minutes?
Multiply by 60, the minutes in an hour. So 2.5 h is 150 min and 1.5 h is 90 min. Choose hours above and every other unit comes back at once, with the working shown.
How do I convert minutes to hours?
Divide by 60. So 90 min is 1.5 h - one and a half hours, which is 1 hour 30 minutes, not 1 hour 50 minutes.
How do I convert seconds to hours and days?
Divide by 3,600 for hours and by 86,400 for days. So 1,000,000 s is 277.7778 h, or 11.57407 d, each shown to seven significant figures.
How many days are in a year and in a month here?
A year here is the average Gregorian year, 365.2425 days, because 97 years in every 400 are leap years. A month is a twelfth of that, 30.436875 days, shown as 30.43688. So 1 yr is exactly 12 mo, 8,765.82 h and 31,556,952 s.
How many weeks are in a year?
An average year of 365.2425 days is 52.1775 weeks - a little more than 52, because 52 weeks are only 364 days.
Can I count the days between two dates here?
No. This converts a length of time from one unit to another, using average months and years. Real months run 28 to 31 days and real years 365 or 366, so counting between two actual dates needs a date calculator, such as the age calculator.