Time Conversion Calculator
Convert between twelve units of time, from nanoseconds to centuries, in one step. Enter a value, pick your from and to units, and the tool converts instantly. It also renders your result in every other unit at the same time, so one input answers every follow-up question.
Time Conversion Calculator
Twelve units, from nanoseconds to centuries
Enter a number greater than or equal to 0.
| Unit | Your value equals |
|---|
Quick Answer
How the conversion works
Every unit is defined by a single exact factor relative to the second: 1 minute = 60 seconds, 1 hour = 3,600 seconds, 1 day = 86,400 seconds, 1 week = 604,800 seconds. The tool multiplies your value into seconds, then divides by the target unit’s factor. Because the whole calculation runs through one common base, there is no rounding drift between units: converting hours to minutes and then minutes to seconds gives exactly the same answer as converting hours to seconds directly.
The page shows its working on every calculation. Converting 2 hours to minutes displays the formula line “Working: 2 × (3600 s per h ÷ 60 s per min) = 120 minutes”, so you can see exactly which factors were used. The results table then renders the same input in all twelve units, from nanoseconds to centuries.
Worked example, verified against the tool
- Convert 2 hours to minutes. Seconds per hour = 3,600, seconds per minute = 60. So 2 × (3,600 ÷ 60) = 2 × 60 = 120 minutes.
- The tool shows exactly this, plus the same 2 hours expressed in every other unit: 7,200 seconds, 0.08333333333 days, 0.0119047619 weeks, 0.002737850787 months (average), 0.0002281542323 years (average), and 7,200,000 milliseconds.
- A second check: 1,000,000 seconds to days = 1,000,000 ÷ 86,400 = 11.57407407 days, matching the tool output.
- Both examples were run through the live calculator code (with the documented month fix below) and confirmed.
Reading your results
The tool formats numbers so the table stays readable without hiding precision. Results keep up to 10 significant figures, which is why 1,000,000 seconds renders as 11.57407407 days rather than a shorter rounded value. Very large or very small results switch to exponential notation: a century in nanoseconds shows as 3.1558e+18 instead of a 19-digit string. Zero always renders as plain 0.
One display detail worth knowing: the “Working” formula line shows the parsed value of your input, not exactly what you typed. If you enter 1e3 minutes, the tool reads it as 1000 and the formula line says “Working: 1000 × …” accordingly. The copy button copies the headline result and the working line; the full twelve-unit table stays on the page.
The honest part: months and years are averages
Seconds, minutes, hours, days, and weeks are exact by definition. Months and years are not: February has 28 or 29 days, and a year can be 365 or 366 days. This tool uses the standard averages, 1 month = 30.4375 days (365.25 ÷ 12) and 1 year = 365.25 days, and labels them as averages in the dropdown so nobody mistakes them for calendar-exact values. If your calculation depends on a specific month or a leap year, convert with days instead and pick the exact day count yourself.
One correction worth knowing: the previous version of this tool defined a month as 2,629,746 seconds (a Gregorian-mean-year month) while the year used 31,557,600 seconds (a 365.25-day year), so converting 12 months gave 0.9999794661 years. That was internally inconsistent, so the month constant is now exactly one-twelfth of the year (2,629,800 seconds): 12 months convert to exactly 1 year, and 1 month converts to exactly 30.4375 days.
Common conversions at a glance
| From | To | Multiply or divide by |
|---|---|---|
| Minutes | Seconds | × 60 |
| Hours | Minutes | × 60 |
| Days | Hours | × 24 |
| Weeks | Days | × 7 |
| Seconds | Milliseconds | × 1,000 |
| Hours | Seconds | × 3,600 |
| Days | Months (average) | ÷ 30.4375 |
| Days | Years (average) | ÷ 365.25 |
When a conversion needs a calendar-exact answer rather than an average, work in days. For adding up several durations rather than converting one, the time length calculator is the right tool. Single-pair conversions live on their own pages too: hours to days, minutes to hours, and months to years.
What competing calculators miss
Most time converters stop at six or seven units and answer only the single pair you asked about, so the next obvious question (“and in weeks?”) sends you back to the form. The usual gaps are units above years (decades and centuries are missing from several rivals), an all-units table shown at the same time as the headline answer, a visible working line that shows the exact factors used, and a month definition that actually agrees with the year definition. This page ships twelve units from nanoseconds to centuries, renders all twelve on every conversion, shows the working formula each time, labels months and years as averages in the dropdown itself, and now defines the month as exactly one-twelfth of the 365.25-day year so 12 months convert to precisely 1 year.
Frequently asked questions
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References
- Bureau International des Poids et Mesures. SI base units: the second as the SI base unit of time. Accessed 2026-10-24.
- National Institute of Standards and Technology. Definitions of the SI base units: the second defined by the caesium-133 hyperfine transition frequency. Accessed 2026-10-24.
- National Institute of Standards and Technology. Time and Frequency Division: how official time scales are maintained. Accessed 2026-10-24.
- International Earth Rotation and Reference Systems Service. Bulletin C: leap second announcements: why leap seconds are excluded from fixed-factor conversion. Accessed 2026-10-24.
- International Astronomical Union. Recommendations concerning units: the Julian year of exactly 365.25 days used for the average year. Accessed 2026-10-24.