Time Converter

Convert between seconds, minutes, hours, days, weeks, months, years, and beyond — across the sexagesimal and decimal boundaries that trip people up.

Time

seconds → millennia

From

Result

1000

1 s = 1000 ms

Popular conversions

What Is a Time Converter?

A time converter translates a duration from one unit to another — seconds to hours, days to weeks, minutes to milliseconds. Time is unusual because its everyday units aren't decimal: 60 seconds to a minute, 60 minutes to an hour, 24 hours to a day, 7 days to a week. That base-60 (sexagesimal) and base-24 mix, inherited from ancient Babylon and Egypt, is exactly why duration math is so error-prone and a converter so useful.

This converter works from the second, the SI base unit of time, defined since 1967 by the vibrations of a caesium atom. Larger units build up from there, and the tool also handles the fuzzy big units — a 'month' averages 30.44 days and a 'year' 365.25 days — so long-span conversions stay consistent.

This is one category of the full Unit Converter — pair it with our percentage calculator or scientific calculator for related everyday maths.

How Time Conversion Works

Everything routes through the second

Each unit has a fixed second count. The converter turns your input into seconds, then divides by the target unit's seconds, keeping all outputs consistent.

Small units are sexagesimal

60 seconds per minute, 60 minutes per hour. This base-60 system means 90 minutes is 1.5 hours, not 1.3 — the classic decimal-versus-clock confusion.

Days and weeks are clean

24 hours per day, 7 days per week. These steps are fixed and exact, so day- and week-level conversions are straightforward.

Months and years are averaged

Calendar months vary (28–31 days), so a generic 'month' is taken as 30.44 days and a 'year' as 365.25 days to account for leap years.

Core Time Conversion Factors

Multiply to reach seconds; divide to come back. The small units are base-60, not base-10.

Hours → seconds

× 3600

One hour is 60 × 60 = 3,600 seconds. The bridge between clock units and SI seconds.

Days → hours

× 24

One day is 24 hours. Combine with the hour factor: one day is 86,400 seconds.

Years → days

× 365.25

An average year is 365.25 days, including the quarter-day that leap years correct for.

How to Use the Time Converter

1
Enter the duration
Type the length of time you want to convert — a runtime, a deadline span, a process duration.
2
Choose the 'from' unit
Pick seconds, minutes, hours, days, weeks, months, or years as your starting unit.
3
Choose the 'to' unit
Select the target unit, or swap the two to reverse direction.
4
Read every unit at once
The all-units table shows the duration in seconds, minutes, hours, days, and beyond simultaneously.

Key Time Concepts

The second

The SI base unit of time, defined since 1967 by 9,192,631,770 oscillations of a caesium-133 atom — the most precisely realised unit in all of measurement.

Sexagesimal units

Minutes and hours use base 60, inherited from Babylonian astronomy. It's why clock time doesn't map cleanly onto decimal fractions.

Average month and year

Because calendar months differ, a generic month is 30.44 days and a year 365.25 days. Specific dates need a calendar, not an average.

Leap year correction

Earth's orbit is ~365.25 days, so we add a leap day every four years. The 365.25-day average bakes that correction into long conversions.

Real-World Time Conversions

⏱️

Decimal vs clock minutes

1.5 hours is 90 minutes, but 1.5 hours is often misread as 1 h 30 min written '1.30' — the most common everyday time slip.

💼

Billable hours

A 45-minute task is 0.75 hours for invoicing; 7.5 hours is a standard workday. Timesheets convert clock time to decimal hours.

📅

Project deadlines

A 6-week project is 42 days or about 1.4 months. Planning tools convert between weeks, days, and months for scheduling.

🎬

Media runtimes

A 7,200-second video is exactly 2 hours; a 90-minute film is 5,400 seconds. Encoding and editing tools work in seconds.

🏃

Race and split times

A 3-hour marathon is 180 minutes or 10,800 seconds. Pace math converts total time into per-kilometre or per-mile splits.

🚀

Mission and uptime

A 1,000-hour server uptime is 41.7 days; a 6-month mission is about 182 days. Long-duration tracking spans hours to months.

Best Practices for Time Conversion

✓Don't read decimal hours as clock minutes. 1.5 hours is 1 h 30 min, not 1 h 5 min; 2.75 hours is 2 h 45 min. Decimal fractions of an hour aren't minutes — multiply the fraction by 60.
✓Use averaged months and years for spans. For generic durations, treat a month as 30.44 days and a year as 365.25 days. For specific calendar dates, use a date calculator instead.
✓Work in seconds for code and precision. Timestamps, encoders, and physics calculations use seconds (or milliseconds). Convert to seconds, compute, then convert back for display.
✓Mind leap years over long spans. The 365.25-day year accounts for leap days on average; exact multi-year date math still needs a calendar that knows which years are leap.
✓Keep units explicit in schedules. '2' could be hours, days, or weeks. Always label the unit in plans and timesheets so a duration isn't read at the wrong scale.

Common Time Conversion Mistakes

Treating 1.30 hours as 1 h 30 min

1.30 hours is 1 hour 18 minutes (0.30 × 60), while 1 h 30 min is 1.5 hours. The decimal point and the clock colon are different scales.

Using base-10 for minutes and hours

Minutes and hours are base-60. Dividing seconds by 100 instead of 60 to get minutes is a frequent and significant error.

Assuming every month is 30 days

Calendar months range 28–31 days. For generic spans use 30.44 days; for real dates use an actual calendar, not a flat 30.

Ignoring leap days over years

A flat 365-day year drifts by a day every four years. Long-span conversions should use 365.25 days to stay accurate.

Why Time Conversion Matters

Time underpins scheduling, billing, media, science, and software — and its non-decimal units make it one of the easiest measurements to get wrong. The gap between '1.5 hours' and a misread '1 hour 30 written as 1.30' has thrown off invoices, missed deadlines, and broken automated schedules; the base-60 structure means decimal intuition simply doesn't apply.

At the technical end, nearly everything computational runs on seconds or milliseconds, while humans think in hours, days, and weeks — so conversion is the constant bridge between the two. A converter that routes through the second and handles the sexagesimal steps and averaged months and years keeps timesheets, project plans, and code in agreement.

Built for project planners, freelancers billing hours, developers, editors, athletes, and anyone converting durations across units.

Linear unit factors follow the BIPM SI brochure, the NIST Guide to the SI, and ISO 80000. Currency rates load live from open.er-api.com; crypto prices from CoinGecko. See our methodology and editorial policy. Educational only — not certified for regulated trading, settlement, medical, or aerospace use.

Time Converter FAQs

There are 3,600 seconds in an hour, because an hour is 60 minutes and each minute is 60 seconds (60 × 60 = 3,600). A full day is 24 × 3,600 = 86,400 seconds. These base-60 and base-24 steps are why time math doesn't follow decimal intuition.

Divide minutes by 60. So 90 minutes is 90 ÷ 60 = 1.5 hours, and 45 minutes is 0.75 hours. A common mistake is writing 1 hour 30 minutes as '1.30 hours' — but 1.30 hours is actually 1 hour 18 minutes. Decimal hours and clock minutes are different scales.

This converter uses 365.25 days for an average year, which accounts for the leap day added every four years. A common (non-leap) calendar year is 365 days and a leap year is 366. For exact spans between real dates, use a date calculator instead of an average.

Calendar months range from 28 to 31 days, so for generic conversions an average month is taken as 30.44 days (365.25 ÷ 12). If you need the exact length of a specific month, count the calendar days rather than using the average.

Our minute and hour units are base-60 (sexagesimal), inherited from Babylonian astronomy, and days use base-24. Decimal time has been proposed (and briefly tried in revolutionary France) but never stuck. This is why a time converter is so useful — the mixed bases defeat simple mental decimal math.

It routes every conversion through the SI second at full precision, using exact small-unit steps (60, 60, 24, 7) and standard averages (30.44-day month, 365.25-day year). Results are exact to your input precision for fixed units, and consistent for the averaged month and year.