Time calculators

Times Calculator

Updated Sep 19, 2026 By Infinity Calculator
Rate Formulas

Add or Subtract Two Time Durations

 
Days
Hours
Minutes
Seconds
Time A
Operation applied to Time A and Time B
Time B
Result
0 d 0 h 0 m 0 s
Total in days
0
Total in hours
0
Total in minutes
0
Total in seconds
0
Headline total
0 hours
Step-by-Step Solution
Time A vs Time B vs Result

Expression Time Calculator (type a chained duration)

Format: 1d 2h 30m 45s + 3h 15m – 90s — units: d days, h hours, m minutes, s seconds. Decimals such as 1.5h are allowed.
 
Days
Hours
Minutes
Seconds
Result
0 d 0 h 0 m 0 s
Total in days
0
Total in hours
0
Total in minutes
0
Total in seconds
0
Terms detected
—
Step-by-Step Solution
Contribution of each term

Introduction

This time calculator adds and subtracts time. You type days, hours, minutes, and seconds, and it returns the answer. It works in time units instead of plain numbers, so you do not have to carry 60s and 24s in your head.

There are two ways to use it. The first panel lets you enter two times, pick add or subtract, and see the result. The second panel lets you type a whole line like 1d 2h 30m + 4h 15m 20s - 2500s and solves the full chain at once.

The tool also shows your total in days, hours, minutes, and seconds, plus a step-by-step solution and a bar chart. If the answer is less than zero, it tells you that too. Use it for work hours, travel time, cooking, workouts, video lengths, or any other time math.

How to use our Time Calculator

Type in two time amounts, pick add or subtract, and the calculator shows the answer in days, hours, minutes, and seconds, plus the total in one unit and the steps used to get there.

Time A (Days, Hours, Minutes, Seconds): Enter the first time span. Put each part in its own box. Leave a box blank or use 0 if you do not need it. Decimals like 1.5 are fine.

Operation: Click Add to join the two times together, or Subtract to take Time B away from Time A.

Time B (Days, Hours, Minutes, Seconds): Enter the second time span the same way. If the answer is below zero, the calculator marks it as negative and tells you how much bigger Time B is.

Chart & headline unit: Pick seconds, minutes, hours, days, or weeks. This changes the big total shown and the bars in the chart.

Calculate and Clear buttons: Press Calculate to see the result, or Clear to empty every box and start over.

Time expression box: In the second panel, type a chain of times like 1d 2h 30m + 4h 15m − 90s. Use d for days, h for hours, m for minutes, and s for seconds. You can add as many plus and minus terms as you want.

Chart unit (expression panel): Choose the unit used to draw each term on the bar chart, so you can see which part adds or removes the most time.

Time Arithmetic: Adding and Subtracting Time

Time math means adding or subtracting amounts of time, like days, hours, minutes, and seconds. It is not like normal math, because time does not use groups of ten. Minutes and seconds roll over at 60, and hours roll over at 24. So 45 minutes plus 30 minutes is not 75 minutes. It is 1 hour and 15 minutes.

How Time Units Work Together

Every time unit can be turned into seconds. That makes the math simple and safe.

  • 1 minute = 60 seconds
  • 1 hour = 60 minutes = 3,600 seconds
  • 1 day = 24 hours = 1,440 minutes = 86,400 seconds
  • 1 week = 7 days = 604,800 seconds

The Easy Method

The standard method has three steps:

  1. Convert. Change each time into total seconds.
  2. Add or subtract. Work with plain numbers, so no carrying rules get in the way.
  3. Normalize. Break the answer back into days, hours, minutes, and seconds. Divide by 86,400 for days, then 3,600 for hours, then 60 for minutes. Whatever is left over is seconds.

For example, 5 hours 30 minutes is 19,800 seconds. Add 20 hours 45 minutes (74,700 seconds) and you get 94,500 seconds. That is 1 day, 2 hours, 15 minutes.

Carrying and Borrowing

If you add time column by column, you must carry. When seconds pass 60, move 1 to the minutes. When minutes pass 60, move 1 to the hours. When hours pass 24, move 1 to the days. Subtracting works the other way. If you do not have enough seconds, borrow 60 from the minutes. If you do not have enough minutes, borrow 60 from the hours.

Negative Results

If you take away more time than you started with, the answer is negative. That is fine. A negative answer just tells you how much bigger the second time was. For example, 2 hours minus 5 hours equals −3 hours.

Where People Use Time Math

  • Work hours: adding up shifts and breaks to find total pay time.
  • Sports and racing: finding lap times, splits, and gaps between runners.
  • Cooking and baking: adding prep time, cook time, and rest time.
  • Travel: adding flight time, layovers, and drive time.
  • Video and audio: adding clip lengths to get a total run time.
  • School and study plans: adding up hours spent on each subject.

Duration vs. Clock Time

A duration is a length of time, like "3 hours 20 minutes." A clock time is a point in the day, like "4:15 PM." This page works with durations. You can add and subtract them freely, and they can be longer than 24 hours without rolling over to a new date.

Quick Tips

  • Decimal hours are common in pay sheets. 1.5 hours means 1 hour 30 minutes, not 1 hour 50 minutes.
  • To change minutes into decimal hours, divide by 60. So 45 minutes = 0.75 hours.
  • To change decimal hours into minutes, multiply by 60. So 0.4 hours = 24 minutes.
  • Always use the same unit on both sides before you add or subtract.

Formulas used

Convert a duration to total seconds
T = (d \times 86400) + (h \times 3600) + (m \times 60) + s
Add or subtract two durations
T = T_A \pm T_B
Sum of signed expression terms
T = \sum_{i=1}^{n} \sigma_i T_i, \quad \sigma_i = \pm 1
Normalize total seconds into days, hours, minutes, seconds
d = \left\lfloor \frac{|T|}{86400} \right\rfloor,\quad h = \left\lfloor \frac{|T| - 86400d}{3600} \right\rfloor,\quad m = \left\lfloor \frac{|T| - 86400d - 3600h}{60} \right\rfloor,\quad s = |T| - 86400d - 3600h - 60m
Total expressed in a single unit
T_{\text{unit}} = \frac{T}{f},\quad f \in \{1,\ 60,\ 3600,\ 86400,\ 604800\}
Totals in days, hours, minutes and seconds
T_{d} = \frac{T}{86400},\quad T_{h} = \frac{T}{3600},\quad T_{m} = \frac{T}{60},\quad T_{s} = T

Frequently asked questions

How do you add hours and minutes together?

Add each unit on its own, then fix anything that goes over its limit.

  1. Add the seconds. If you get 60 or more, take away 60 and add 1 minute.
  2. Add the minutes. If you get 60 or more, take away 60 and add 1 hour.
  3. Add the hours. If you get 24 or more, take away 24 and add 1 day.

Example: 2h 45m + 1h 30m = 3h 75m. Since 75 minutes is over 60, it becomes 4h 15m.

How do you subtract time when there are not enough minutes or seconds?

You borrow, just like in regular subtraction, but you borrow 60 instead of 10.

  • Not enough seconds? Take 1 minute and add 60 seconds.
  • Not enough minutes? Take 1 hour and add 60 minutes.
  • Not enough hours? Take 1 day and add 24 hours.

Example: 5h 10m − 2h 40m. Borrow an hour: 4h 70m − 2h 40m = 2h 30m.

Why can't you add time like normal numbers?

Normal numbers roll over at 10. Time does not. Seconds and minutes roll over at 60, hours roll over at 24, and days roll over at 7 for weeks.

That is why 1.45 plus 1.30 on a phone gives 2.75, but 1h 45m plus 1h 30m gives 3h 15m. The units are different sizes, so you must carry at 60 and 24.

How many seconds are in a minute, hour, day, and week?

  • 1 minute = 60 seconds
  • 1 hour = 3,600 seconds
  • 1 day = 86,400 seconds
  • 1 week = 604,800 seconds

Turning every time into seconds first is the safest way to add or subtract. Seconds are plain numbers, so no carrying rules get in the way.

How do you turn a big number of seconds into days, hours, and minutes?

Divide in order, from the biggest unit down:

  1. Divide by 86,400 for days. Keep the remainder.
  2. Divide that remainder by 3,600 for hours.
  3. Divide the next remainder by 60 for minutes.
  4. What is left is seconds.

Example: 94,500 seconds = 1 day, 2 hours, 15 minutes.

How do you change minutes into decimal hours?

Divide the minutes by 60.

  • 15 minutes ÷ 60 = 0.25 hours
  • 30 minutes ÷ 60 = 0.5 hours
  • 45 minutes ÷ 60 = 0.75 hours
  • 20 minutes ÷ 60 = 0.333 hours

To go the other way, multiply the decimal by 60. So 0.4 hours × 60 = 24 minutes.

What does 1.5 hours mean in hours and minutes?

1.5 hours means 1 hour and 30 minutes, not 1 hour and 50 minutes. The .5 is half of an hour, and half of 60 minutes is 30.

Multiply the part after the dot by 60 to get minutes. So 2.25 hours = 2 hours 15 minutes, and 3.75 hours = 3 hours 45 minutes.

Can a time answer be negative?

Yes. If you take away more time than you started with, the answer goes below zero. A negative answer just shows how much bigger the second time was.

Example: 2 hours − 5 hours = −3 hours. That means the second time is 3 hours longer. It is common when you compare a planned time against a real time.

How do you add up hours on a timesheet?

Add each shift as hours and minutes, carrying 60 minutes into 1 hour. Then subtract unpaid breaks.

Example: 8h 15m + 7h 50m + 6h 20m = 22h 25m. Take out a 30 minute break each day (1h 30m) and you get 20h 55m.

For pay, change the minutes into decimals: 55 minutes ÷ 60 = 0.92, so 20.92 hours.

How do you multiply a time duration?

Change the time into one unit first, usually seconds or minutes. Multiply, then break the answer back down.

Example: 1h 20m × 3. That is 80 minutes × 3 = 240 minutes, which is 4 hours.

Dividing works the same way. 4h 30m ÷ 4 = 270 minutes ÷ 4 = 67.5 minutes = 1h 7m 30s.

What is the difference between a duration and a clock time?

A duration is how long something lasts, like "3 hours 20 minutes." A clock time is a point in the day, like "4:15 PM."

Durations can be added and subtracted freely, and they can go past 24 hours without becoming a new date. Clock times wrap around at midnight, so 11 PM plus 3 hours lands at 2 AM the next day.

How many days is 100 hours?

100 hours is 4 days and 4 hours. Divide 100 by 24 to get 4 full days, with 4 hours left over.

The same trick works for any hour count: divide by 24 for days, and the remainder is the extra hours. For example, 60 hours = 2 days 12 hours.

How do you round time to the nearest quarter hour?

Quarter hours are 15 minutes each: :00, :15, :30, and :45. Round the minutes to whichever one is closest.

  • 1 to 7 minutes past rounds down
  • 8 to 14 minutes past rounds up

So 8:07 becomes 8:00, and 8:08 becomes 8:15. Many payrolls use this rule, often called the 7 minute rule.

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