Time Duration Calculator

Add or subtract two durations given in hours and minutes — useful for scheduling, cooking, or stacking time blocks.

Calculating how much time sits between two points looks like basic subtraction until you actually try to do it across hours and minutes together — 5:45 minus 2:20 isn't a clean subtraction the way 545 minus 220 would be, because time doesn't work in base ten. Sixty minutes make an hour, not a hundred, which means any duration calculation spanning an hour boundary requires "borrowing" in a way that trips people up specifically because the rest of arithmetic doesn't work that way.

That mismatch between how we write time (hours and minutes, base 60) and how we're taught to do subtraction (base 10) is the entire reason duration calculators exist as their own category of tool rather than something everyone just does in their head reliably. It's not that the math is conceptually hard — it's that the borrowing rule is easy to get wrong under normal conditions, and even easier to get wrong when you're doing it quickly or under time pressure, which is often exactly when you need the answer.

This tool handles that conversion directly: enter a start and end time, and it calculates the exact duration between them in hours and minutes, correctly handling the borrowing across the hour boundary so you don't have to do it by hand.

1. Enter the first duration in hours and minutes.
2. Choose Add or Subtract.
3. Enter the second duration.
4. Press Calculate to see the result.