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Time Unit Converter

Convert between milliseconds, seconds, minutes, hours, days, weeks, average months, years, decades and centuries, with an hours:minutes:seconds breakdown.

Level: Grades 4–5

  • Common Core standard 4.MD.A.1Know relative sizes of measurement units within one system of units including km, m, cm; kg, g; lb, oz.; l, ml; hr, min, sec. Within a single system of measurement, express measurements in a larger unit in terms of a smaller unit. Record measurement equivalents in a two-column table.
  • Common Core standard 5.MD.A.1Convert among different-sized standard measurement units within a given measurement system (e.g., convert 5 cm to 0.05 m), and use these conversions in solving multi-step, real world problems.
Printable worksheet

Time Unit Converter

Know the answer you need? Pick an input to work backward.

Inputs

Result

In hours

1.5 h

90 min = 1.5 h

As hours:minutes:seconds
1:30:00
As days, hours, minutes and seconds
0 d 1 h 30 min 0 sSeconds are rounded to the nearest millisecond.

See the step-by-step solution ↓

90 min in every unit
90 min in every unit
UnitValue
Milliseconds (ms)5,400,000
Seconds (s)5,400
Minutes (min)90
Hours (h)1.5
Days (d)0.0625
Weeks (wk)0.008929
Months (average) (mo)0.002053
Years (Gregorian average) (yr)0.000171
Decades (decades)0.000017
Centuries (centuries)0.000002

Step-by-step solution

  1. First change to seconds, the shared unit: 1 minute = 60 s, so multiply

    90 min×60=5,400 s

  2. Then change to hours: 1 hour = 3,600 s, so divide by that

    5,400 s3,600=1.5 h

  3. Split the total seconds into whole hours, then whole minutes, then the seconds left over

    5,400 s=1 h 30 min 0 s=1:30:00

  4. Take whole days (24 hours each) out of the hours as well

    1 h=0 d 1 h=0 d 1 h 30 min 0 s

Test yourself

20 quick questions built from this calculator's formula: work out results, predict what happens when an input changes, and work backward from an answer. Every answer comes with the working.

What this calculator does

Turn any length of time into the unit you need, from milliseconds up to centuries. Seconds, minutes, hours, days and weeks always have the same length. So converting between them is just multiplying or dividing. Months and years are trickier. A calendar month runs from 28 to 31 days, and a year has 365 or 366 days. For those, this tool uses the long-run average of our everyday (Gregorian) calendar. It tells you so in the working.

Enter a length of time. Then pick the unit you have and the unit you want. You get the converted value and a table showing it in every unit. You also see the same time written as hours:minutes:seconds, and as days, hours, minutes and seconds.

Where it's used

Why this math matters outside the classroom:

  • Project planning. A task estimated at 90 minutes is 1.5 hours.
  • Work hours. A 40-hour work week is 40 × 60 = 2,400 minutes.
  • Video length. A recording of 7,384 seconds runs 2 h 3 min 4 s.
  • Page load times. A page that takes 250 ms to load takes a quarter of a second.
  • Long durations. Students find that a 30-day stretch is 720 hours by multiplying by 24.

Grade level and standards: Grades 4–5; Common Core State Standards for Mathematics 4.MD.A.1, 5.MD.A.1. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.

How to use it

  1. Enter the amount of time. Decimals are allowed, such as 2.75 hours.
  2. Choose the unit you have and the unit you want.
  3. Read the converted value. Below it, the h:m:s and day breakdowns show the same span in clock form, and the table lists every unit.

What the inputs mean

Time
The length of time to convert. Negative values are not accepted.
From
Months and years are calendar averages: a year is 365.2425 days and a month is one twelfth of that, 30.436875 days.
To
The unit you want. For a specific stretch of the calendar, such as March to June, count the actual days instead.

Formula and method

result = value × (from-unit in s) ÷ (to-unit in s)
1 min = 60 s;  1 h = 3,600 s;  1 day = 86,400 s;  1 week = 604,800 s
1 year = 365.2425 days = 31,556,952 s  (Gregorian average)
1 month = 1 year ÷ 12 = 30.436875 days = 2,629,746 s
1 decade = 10 years;  1 century = 100 years

In the first line, "value" is the amount you typed. "From-unit in s" is how many seconds one of your starting unit holds, and "to-unit in s" is the same for the unit you want. The Gregorian calendar adds a leap day every fourth year. It skips it in century years that can't be divided evenly by 400. That gives 97 leap days every 400 years, so the average year is 365 + 97/400 = 365.2425 days. Dividing by 12 gives an average month of 30.436875 days.

The converter knows every unit by its length in seconds. It multiplies by the length of the unit you have, then divides by the length of the unit you want. For the breakdown, it rounds the total seconds to the nearest millisecond. Then it splits them into whole hours, minutes and seconds. Last, it takes whole days out of the hours.

Worked example

A film runs 90 minutes. How many hours is that?

  1. 90 min × 60 = 5,400 s.
  2. 5,400 s ÷ 3,600 = 1.5 h.
  3. 5,400 s splits into 1 h 30 min 0 s, written 1:30:00.

Result: 90 minutes is 1.5 hours, or 1:30:00.

Understanding the result

Decimal hours and clock time are easy to confuse: 1.5 hours is 1 hour 30 minutes, not 1 hour 50 minutes. The h:m:s result removes that ambiguity.

Conversions with months or years are averages. 18 months comes out as exactly 1.5 years. But a real 18-month stretch on the calendar may be a day or two longer or shorter than 1.5 average years.

Assumptions and limitations

  • A day is exactly 86,400 seconds. Leap seconds (the odd extra second timekeepers sometimes add) are ignored.
  • Months and years use the Gregorian averages above, not any specific calendar month or year.
  • It does not count real calendar dates; use a date difference calculator for that.
  • The h:m:s breakdown is shown for spans up to about 317,000 years and rounds to the millisecond.
  • Time zones and daylight saving changes are not considered.

Frequently asked questions

How many days are in a month for this converter?

30.436875 days, the average Gregorian month. Real months have 28, 29, 30 or 31 days. The average is the right choice for turning a length of time like "36 months" into years. It's not the right choice for counting days between two dates.

Why is a year 365.2425 days and not 365.25?

365.25 days is the average for the older Julian calendar, which had a leap year every four years. The Gregorian calendar skips three of those leap years every 400 years (1700, 1800 and 1900, for example). That brings the average down to 365.2425 days.

How do I convert decimal hours to hours and minutes?

Keep the whole hours and multiply the decimal part by 60. For 2.4 hours, 0.4 × 60 = 24, so it is 2 hours 24 minutes. The h:m:s result does this for you.

How many weeks are in a year?

An average Gregorian year is 365.2425 ÷ 7 = 52.1775 weeks. A common year of 365 days is 52 weeks and 1 day.

How this calculator is checked

Method: SI second; exact minute, hour, day and week; Gregorian calendar average year (365.2425 days) and month (one twelfth of a year). The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.

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