Time Conversion Calculator
Turn hours, days, weeks and seconds into each other in one step
Time conversion FAQ
What’s the difference between duration and clock time?
This calculator works with durations (how long something lasts), not clock timestamps. For example, “2.5 hours” or “3 days” are durations. Those can be converted cleanly into minutes, seconds, weeks and so on. Calendar-aware things like “from March 1 to April 10” depend on dates, time zones and daylight saving, which are handled by a different type of tool.
How many seconds are in an hour or a day?
By definition, 1 minute = 60 seconds, 1 hour = 60 minutes and 1 day = 24 hours. That gives:
- 1 hour = 3,600 seconds.
- 1 day = 24 × 3,600 = 86,400 seconds.
- 1 week = 7 days = 604,800 seconds.
The calculator uses those exact values whenever it converts between seconds, minutes, hours, days or weeks.
Why are months and years not exact?
Months and years are averages because the calendar is based on Earth’s orbit. A common convention in time-conversion tables is:
- 1 year ≈ 365.2425 days.
- 1 month ≈ 30.436875 days (1/12 of a year on average).
This tool follows that convention for duration maths, which is fine for planning, budgeting and rough estimates. Calendar-specific questions (like “same date next year”) should still use a date-aware tool.
Can I convert very small time slices like microseconds?
Yes. The calculator supports milliseconds (ms), microseconds (µs) and nanoseconds (ns). These are common in programming, profiling, hardware timing, embedded systems and networking, where events are measured in tiny slices of time.
What are good units for projects, workouts or study plans?
For day-to-day planning, hours and days are usually enough: “2.5 hours of study” or “10 days left”. For longer timelines, weeks, months and years make mental math easier. The calculator lets you bounce between those scales so you can express the same duration with whatever unit feels most natural for your task.
Is this accurate enough for billing and time tracking?
Internally, everything uses seconds as the base unit with consistent factors, then gets rounded for display. That’s more than enough for timesheets, project tracking and invoices. If you bill by very strict rules (like rounding up to the nearest 6 minutes), use this tool as the maths engine and then apply your rounding rules on top.
From quick seconds to century-scale timelines
This time conversion calculator gives you one clean line that translates any duration into another unit. Type a value, choose what it’s in (for example hours, days, weeks or years), pick what you want it in (minutes, seconds, months, milliseconds and so on) and the result box shows “X unit = Y unit”. It’s ideal for comparing estimates, splitting tasks into blocks, or understanding how long something really is.
1. Choose the scale that fits your task
The dropdowns cover time units from tiny to huge:
- Centuries (c) and decades for long historical or financial timelines.
- Years and months for planning studies, careers, loans or long projects.
- Weeks and days for sprints, trips, challanges and release windows.
- Hours and minutes for meetings, deep work blocks and workouts.
- Seconds, milliseconds, microseconds and nanoseconds for code, benchmarks and hardware timing.
You can mix and match any pair: weeks to hours, years to seconds, minutes to milliseconds, centuries to days, or microseconds to seconds.
2. Base-unit method: everything through seconds
Internally, the calculator uses seconds as the base unit. Each time unit has a fixed factor that tells the tool how many seconds it represents. Some key ones are:
- 1 minute = 60 s.
- 1 hour = 3,600 s.
- 1 day = 86,400 s.
- 1 week = 604,800 s.
- 1 month ≈ 2,629,746 s (about 30.436875 days).
- 1 year ≈ 31,556,952 s (about 365.2425 days).
- 1 decade = 10 years ≈ 315,569,520 s.
- 1 century = 100 years ≈ 3,155,695,200 s.
- 1 millisecond = 0.001 s, 1 microsecond = 0.000001 s, 1 nanosecond = 0.000000001 s.
When you hit Convert, your input is multiplied by the “to seconds” factor, then divided by the target unit’s factor. That keeps all conversions internally consistent.
3. Time conversion relationships at a glance
This table pulls out some of the common duration relationships the calculator uses, so you can sanity-check results or do fast mental math when you just need an approximate answer.
| Starting Unit | Resulting Unit | Relationship |
|---|---|---|
| Everyday planning | ||
| hours (h) | minutes (min) | 1 h = 60 min |
| hours (h) | seconds (s) | 1 h = 3,600 s |
| days (d) | hours (h) | 1 d = 24 h |
| days (d) | seconds (s) | 1 d = 86,400 s |
| weeks (wk) | days (d) | 1 wk = 7 d |
| Longer-term durations | ||
| months (mo) | days (d) | 1 mo ≈ 30.436875 d |
| years (yr) | days (d) | 1 yr ≈ 365.2425 d |
| decades | years (yr) | 1 decade = 10 yr |
| centuries | years (yr) | 1 century = 100 yr |
| Small technical units | ||
| seconds (s) | milliseconds (ms) | 1 s = 1,000 ms |
| seconds (s) | microseconds (µs) | 1 s = 1,000,000 µs |
| seconds (s) | nanoseconds (ns) | 1 s = 1,000,000,000 ns |
4. Reading and using the result
The result card is intentionally short and readable. If you enter 2.5 and convert from hours to minutes, you’ll see a line like “2.5 h = 150 min”. For productivity or time tracking, that’s all you usually need. If you’re looking at code execution or network latency, converting milliseconds down to micro- or nanoseconds gives you a better feel for how small those numbers really are.
Because everything flows through seconds using consistent factors, the calculator behaves just like a clean duration table, without you needing to remember every factor for weeks, months, years and tiny sub-second units.
References and further reading on time units
These references describe how the core time units and relationships are commonly defined:
- Second — explains the second as the SI base unit of time and how other units relate to it.
- Day — covers the 24-hour day and different definitions used in astronomy and civil timekeeping.
- Year — discusses different year definitions and the commonly used average of about 365.2425 days.
- Orders of magnitude (time) — puts milliseconds, microseconds and nanoseconds in context with everyday and cosmic timescales.
For legal contracts, payroll or billing rules, always check exact cut-offs and rounding policies in your official documentation or local regulations before finalising numbers.