Project Time Calculator

How to Add Hours and Minutes: Carrying, Borrowing and Decimals

The method for adding and subtracting hours and minutes by hand, with worked examples and the mistakes to avoid.

Quick answer

To add hours and minutes, add the minutes first. If they reach 60 or more, subtract 60 and carry 1 to the hours. Then add the hours. For 2 hours 45 minutes plus 3 hours 50 minutes, 45 + 50 = 95, so write 35 and carry 1: the total is 6 hours 35 minutes.

Open the add and subtract time calculator

How to read your result

Time is counted in base 60, not base 10, which is why adding it like ordinary decimals goes wrong. An hour has 60 minutes, so every time the minutes pass 59 you have to move a whole hour across. This guide shows the method for adding, subtracting and converting, with the numbers worked out so you can check yourself. To skip the arithmetic, open the add and subtract time calculator.

There are two common situations. The first is a list of durations you want to total, such as the time spent on several tasks. The second is a clock time plus or minus a duration, such as a meeting that starts at 2:40 PM and lasts 1 hour 35 minutes. The method is the same in both.

The rules for adding and subtracting time

minutes total = m1 + m2 + …    carry = ⌊ minutes total ÷ 60 ⌋    minutes left = minutes total mod 60

hours total = h1 + h2 + … + carry

decimal hours = hours + minutes ÷ 60

To subtract, if the minutes of the first time are smaller than the minutes of the second, take 1 hour from the hours and add 60 to the minutes before subtracting.

Worked examples

Each example uses numbers you can load into the calculator above; the results match the tool exactly.

Example 1: add three durations, 2:45 + 3:50 + 1:20

  • Minutes: 45 + 50 + 20 = 115. That is 1 hour and 55 minutes, so write 55 and carry 1.
  • Hours: 2 + 3 + 1 = 6, plus the carried 1 = 7.
  • Total: 7 hours 55 minutes, which is 7.9167 as a decimal.

Load this example

Example 2: subtract with borrowing, 8:00 − 0:45 − 1:15

  • 8:00 − 0:45: the minutes cannot take 45 from 0, so borrow an hour: 7 hours and 60 minutes. 60 − 45 = 15, so the result is 7:15.
  • 7:15 − 1:15 = 6:00.

Load this example

Example 3: a clock time plus a duration, 2:40 PM + 1:35

Treat the clock time as a duration since midnight, using the 24-hour clock: 14:40 + 1:35.

  • Minutes: 40 + 35 = 75, so write 15 and carry 1.
  • Hours: 14 + 1 + 1 = 16, so the result is 16:15, which is 4:15 PM.

If the hours pass 24, subtract 24 to get the time on the next day.

Load this example

Converting between hours and minutes and decimals

To turn minutes into a decimal, divide by 60: 15 minutes is 0.25, 30 minutes is 0.5, 45 minutes is 0.75 and 20 minutes is 0.33. To turn a decimal back, multiply the part after the point by 60: 0.75 × 60 = 45 minutes. So 7.75 hours is 7 hours 45 minutes. Always convert after adding, not before, because adding rounded decimals accumulates small errors: three times 0.33 is 0.99, not 1.

The calculator has a reference table of every minute from 1 to 60 as a decimal, and a two-way converter. To find the time between two clock times instead of adding durations, use the elapsed time calculator.

Step by step: add 4:50 and 2:35

  1. Add the minutes: 50 + 35 = 85.
  2. Carry: 85 minutes is 1 hour 25 minutes. Write 25, carry 1.
  3. Add the hours and the carry: 4 + 2 + 1 = 7.
  4. Write the answer: 7 hours 25 minutes.
  5. Check with decimals: 4.8333 + 2.5833 = 7.4167 = 7 + 0.4167 × 60 = 7 hours 25 minutes.

Assumptions, limits and common mistakes

Assumptions and limits

  • This guide covers durations. Time zones, daylight saving and dates are separate problems.
  • Totals past 24 hours are kept as hours (30:00), not converted to days.
  • Decimal values are rounded; for payroll check which rounding rule your employer uses.

Common mistakes

  • Carrying at 100 instead of 60. 45 + 50 minutes is 95, which is 1 hour 35 minutes, not 1 hour 95.
  • Reading hours:minutes as a decimal. 6:35 is not 6.35 hours; it is 6.58.
  • Adding rounded decimals. Add in hours and minutes, then convert once.
  • Forgetting to borrow when subtracting, which produces negative minutes.

Frequently asked questions

How do I add hours and minutes together?

Add the minutes, carry every 60 into the hours, then add the hours. 2:45 + 3:50 is 6 hours 35 minutes.

How do I add time on a calculator?

Convert minutes to decimals (divide by 60), add, then convert the fraction back, or use a time calculator that works in hours and minutes directly.

What is 1.5 hours in hours and minutes?

1 hour 30 minutes, because 0.5 × 60 = 30.

How do I subtract time when the minutes are smaller?

Borrow 1 hour from the hours, add 60 to the minutes, then subtract. 8:00 − 0:45 becomes 7:60 − 0:45 = 7:15.

How do I add a time of day and a duration?

Use the 24-hour clock: 14:40 + 1:35 = 16:15, which is 4:15 PM. Subtract 24 if the result passes midnight.

How many minutes is 7.5 hours?

450 minutes: 7.5 × 60.

Last updated 19 October 2026. Formulas and tests: methodology.