About Time Converter
Convert between common time-converter units instantly. Free online converter. Free, no sign-up required.
How to use
- Type your duration into the Value field. Decimals are accepted, so 2.5 hours or 0.25 days both work, and the conversion runs the moment you finish typing.
- Pick the source unit from the From dropdown. Available: milliseconds, seconds, minutes, hours, days, weeks, months (treated as 30 days), and years (treated as 365 days).
- Choose the target unit in the To dropdown. The default pairing is hours-to-minutes for everyday duration math; switch to milliseconds for code timing or to weeks/years for long-horizon planning.
- Use the swap button between the dropdowns to instantly reverse the conversion. Useful for round-tripping an answer back through the inverse factor.
- Read the converted duration in the highlighted result box. Numbers display with up to 4 decimal places — enough for project planning, scientific work, and most code-timing budgets.
- Note that 'Months (30d)' and 'Years (365d)' use rounded calendar averages. For real calendar arithmetic (with leap years, varying month lengths, and time zones) use a date calculator — this tool is for SI-style duration math, not calendar dates.
Examples
Project duration
A 6-week project equals 42 days, 1,008 hours, or 60,480 minutes. At a typical 40-hour work week that is 240 working hours total — a useful sanity check when a stakeholder asks 'how many hours of work is that really?'
Code timing budget
A 60 fps game has 16.667 ms per frame. That equals 16,667 microseconds or 16,666,667 nanoseconds — the budget you have for everything (input, physics, render, audio) before you drop a frame. 144 fps tightens it to 6.944 ms per frame.
Lifespan in seconds
An 80-year human lifespan equals 29,200 days, 700,800 hours, or about 2.523 billion seconds. Carl Sagan's famous 'cosmic calendar' compresses 13.8 billion years of cosmic time into one calendar year, putting all of human civilization into the last 14 seconds of December 31.
Frequently asked questions
How do I convert hours to minutes or seconds?
Multiply hours by 60 to get minutes, or by 3,600 to get seconds. So 2.5 hr = 150 min = 9,000 s. Going the other way, divide minutes by 60 or seconds by 3,600 to recover hours. The factor 3,600 is just 60 (sec/min) × 60 (min/hr). For days: × 86,400 (= 24 × 3,600) to get seconds. These factors are exact by definition — the second is the SI base unit.
How many seconds are in a year?
A 365-day year contains exactly 31,536,000 seconds (365 × 86,400). A 366-day leap year has 31,622,400 seconds. A Julian year (365.25 days) used in astronomy is 31,557,600 seconds. Physicists use the rough approximation π × 10⁷ seconds ≈ 31,415,927 — only 0.4% off from a non-leap year, which makes it a memorable mental shortcut for back-of-envelope calculations.
How do I convert decimal hours to hours and minutes?
Multiply the decimal portion by 60 to get minutes. So 3.75 hr → 0.75 × 60 = 45 min, giving 3 hr 45 min. Conversely, 1 hr 30 min = 1 + 30/60 = 1.5 hr. This crops up constantly in payroll (timesheets in decimal hours but pay periods in hours-and-minutes), in billing (bill in 0.1 or 0.25 hour increments), and in scheduling (meeting blocks rounded to quarter-hours).
What is the difference between a calendar year and a Julian year?
A calendar (Gregorian) year is 365 or 366 days depending on leap year rules; the average over the 400-year cycle is 365.2425 days. A Julian year is exactly 365.25 days — a constant used in astronomy and physics where you do not want leap year discontinuities in your equations. A tropical year (Earth's orbital period relative to the equinoxes) is 365.24219 days. The 0.0078-day gap between Julian and tropical is what motivated the Gregorian reform of 1582.
How is the SI second defined?
Since 1967, the second has been defined as exactly 9,192,631,770 oscillations of the radiation produced by the transition between two hyperfine ground-state energy levels of caesium-133 atoms (at rest, 0 K). This is the basis of atomic clocks — modern caesium fountain clocks reach uncertainties of about 1 part in 10¹⁶, accurate to within 1 second over hundreds of millions of years.
What is a leap second and how does it affect time conversion?
Leap seconds are extra seconds added (or theoretically subtracted) to UTC to keep it aligned with Earth's rotation, which is gradually slowing. Since 1972, 27 leap seconds have been added. They are not in this converter — calendar duration math treats every minute as 60 seconds. For timestamps and astronomical calculations spanning leap-second insertions, use a calendar-aware library. The leap second will be retired around 2035 in favor of larger, less frequent corrections.
Why does this converter treat a month as 30 days and a year as 365 days?
Real calendar months range from 28 to 31 days, and years are 365 or 366 days, so any single conversion factor is an approximation. 30 days is the round-number convention common in finance (loan day-count) and rough planning. 365 days is the non-leap-year average. For exact calendar arithmetic between two specific dates, use a date difference calculator that accounts for actual month lengths and leap years; for back-of-envelope duration math, the rounded factors here are usually fine.
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