Add or subtract hours, minutes, and seconds with precision. Three powerful modes — time adder, date+time offset, and expression mode. Get instant, carry-correct results.
Pick the mode that matches your task — then get an accurate result in seconds with automatic carry-over handling.
Time Adder for totals, Date+Time for finding a future/past moment, or Expression for typed formulas.
Type days, hours, minutes, and seconds into any field. Blank fields default to zero — no errors.
Each row in Time Adder has its own + / − toggle. Mix additions and subtractions freely in one calculation.
Get a full breakdown — days, hours, minutes, seconds — plus totals in seconds, minutes, and hours.
Most online time calculators are clunky, table-based forms from the early 2000s. Here's what we do differently.
Enter 75 minutes and the calculator automatically converts it to 1 hour 15 minutes — no manual math required.
Add as many time rows as you need. Sum ten different work sessions, seven tasks, or an entire project timeline.
Add 36 hours and 45 minutes to any starting date and time to find the exact resulting calendar date and clock time.
Type 2h 30m + 45m - 10s directly — perfect for power users who think in formulas.
Negative values and invalid inputs are caught before calculation. Clear error messages guide you to the correct format.
Every result shows the full decomposed breakdown (d/h/m/s) plus aggregate totals in seconds, minutes, and hours.
Time uses a sexagesimal (base-60) system — not base-10 — which is why adding time values requires special carry-over logic.
A clear reference table for every time unit — from nanoseconds to decades — useful for students, developers, and professionals.
| Time Unit | Equal to (Seconds) | Equal to (Minutes) | Equal to (Hours) | Common Use |
|---|---|---|---|---|
| 1 Second | 1 s | 0.017 min | 0.000278 hr | Base unit, stopwatch |
| 1 Minute | 60 s | 1 min | 0.0167 hr | Short tasks, meetings |
| 1 Hour | 3,600 s | 60 min | 1 hr | Work blocks, travel |
| 1 Day | 86,400 s | 1,440 min | 24 hr | Deadlines, schedules |
| 1 Week | 604,800 s | 10,080 min | 168 hr | Sprint planning |
| 1 Month (avg) | 2,629,800 s | 43,830 min | 730.5 hr | Billing cycles |
| 1 Year (avg) | 31,557,600 s | 525,960 min | 8,766 hr | Contracts, leases |
| 1 Decade | 315,576,000 s | 5,259,600 min | 87,660 hr | Long-term planning |
From tracking work hours to scheduling shifts to solving physics problems — a time calculator is used across almost every field.
Sum multiple work sessions — 1h 45m + 2h 30m + 45m — to calculate exact billable hours for client invoices.
Calculate total weekly hours worked across irregular shifts, or find exactly when a shift ends given a start time and duration.
Solve physics and math problems involving time arithmetic, or calculate total study time across multiple sessions.
Add driving time, loading time, and breaks together to calculate total trip duration and find exact arrival time.
Total up video clip durations, podcast recording blocks, or edit session lengths to track production time accurately.
Add lap times, rest intervals, and training segments to calculate total workout duration and identify personal records.
A time calculator is a free online tool that adds or subtracts time values expressed in days, hours, minutes, and seconds. Unlike regular arithmetic where numbers carry over at powers of ten, time uses a sexagesimal (base-60) system — 60 seconds per minute, 60 minutes per hour, 24 hours per day. This means that adding 45 minutes to 1 hour 25 minutes does not give you "1 hour 70 minutes." The correct answer is 2 hours 10 minutes, because 60 of those 70 minutes carry over into an additional hour.
Our free online time calculator handles all of this automatically. You enter the values, it handles the carry-over, and you get a clean result in the correct format every time.
The Time Adder is the most commonly used mode. It lets you combine multiple time entries — each with its own + or − operator — and returns the total time.
A freelancer worked three sessions on Monday: 1h 45m, 2h 30m, and 0h 50m. They took a 30-minute break. Total billable time?
Enter: +1h 45m / +2h 30m / +0h 50m / −0h 30m
This mode answers a different question: "If I start at a specific date and time, and add (or subtract) a set duration, what is the exact resulting date and time?"
A night-shift worker starts at 10:30 PM on Friday and works 9 hours 45 minutes. What time and day do they finish?
Start: Friday, 22:30 + 9h 45m
Expression Mode lets you type a time formula directly — ideal for users who are comfortable with a text-based syntax and want to enter complex calculations in one line.
Accepted format: Use d for days, h for hours, m for minutes, and s for seconds. Operators are + and - only. Values without a unit are ignored.
Valid examples: 1d 2h + 3h 45m - 30m 10s · 5h 30m + 2h · 90m - 15s
Pro Tip: Expression Mode is especially powerful for video editors and podcast producers who need to sum clip durations quickly. Type all your clip lengths in one line: 12m 34s + 8m 20s + 22m 05s + 5m 48s and instantly get the total runtime.
The most common mistake people make when adding time manually is forgetting to carry over. Here is a breakdown of how the three carry-over boundaries work:
Our calculator applies all three carry-over rules simultaneously so results are always expressed in the simplest, most readable form.
Understanding typical time durations helps you make sense of your calculations. Below are realistic average durations for common activities — useful reference points when totalling time with this calculator:
The way we measure time today traces back thousands of years. The ancient Egyptians were among the first to divide the day into 12 parts using sundials, and 12 parts of night using star patterns — giving rise to the 24-hour day. Around 127 BC, the Greek astronomer Hipparchus standardized these into equal-length hours, laying the foundation for the system we still use.
The base-60 system for minutes and seconds originated with the Babylonians, who also used 60 as the base for their mathematics due to its exceptional divisibility. The number 60 can be divided evenly by 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, and 30 — making it extraordinarily practical for subdividing hours and minutes without fractions.
Today, the second is defined by the cesium atomic clock — measuring exactly 9,192,631,770 oscillations of a cesium-133 atom. This definition keeps global time accurate to within one second over millions of years.
Everything you need to know about adding and subtracting time values online.
Use the Time Adder tab. Enter each time value's hours and minutes in a separate row, set each row's operator to + (Add), then click Calculate. The tool automatically handles carry-over — so 45 minutes + 25 minutes correctly becomes 1 hour 10 minutes, not 70 minutes. You never need to do the carry-over math yourself.
In the Time Adder, click Add Another Time Row for each work session, enter the duration of each session, and set all operators to +. Click Calculate and the result shows your total hours and minutes. This is the most accurate way to add time for freelance invoicing, timesheet reporting, or project tracking.
One hour contains 3,600 seconds (60 minutes × 60 seconds). One full day contains 86,400 seconds (24 hours × 60 minutes × 60 seconds = 24 × 3,600). One week contains 604,800 seconds. These values are shown in the stats strip above the calculator and are always displayed in your result's "Total Seconds" field.
Yes — that's one of this calculator's key improvements over basic tools. In the Time Adder, every row has its own + / − toggle. Set some rows to add and others to subtract in the same calculation. For example: total work session time (+) minus total break time (−) = net productive hours. In Expression Mode, you can mix + and − freely inline: 3h 30m + 45m - 15m 10s.
Time Adder gives you a duration — a total time span (e.g. "4 hours 35 minutes"). Date + Time Offset gives you a specific moment in time — an exact date and clock time (e.g. "Saturday, May 3, 2026 at 08:15 AM"). Use it when you need to know when something ends or begins, not just how long it takes.
Type values followed immediately by their unit letter: d for days, h for hours, m for minutes, s for seconds. Separate terms with + or -. Units within a term can be in any order, though conventional order (d h m s) is recommended. Examples: 2h 30m + 45m · 1d 6h - 2h 30m · 90m + 1h 20m - 15s
Explore more free date and time calculators on SpeedCalculator.net.