Dates & Time

Time Duration Calculator

What this does

Measure the elapsed time between two clock times on the same day, shown as H:MM:SS plus decimal hours for timesheets.

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Runs in your browser

Calculator inputs

How to use it

Using the time duration calculator

  1. 01

    Type both times in HH:MM

    Use 24-hour format with leading zeros, e.g. 08:05 and 17:30.

  2. 02

    Check the order

    The end time must come after the start time on the same day.

  3. 03

    Copy the format you need

    H:MM:SS for readability, decimal hours for payroll systems.

Good to know

Decimal hours versus H:MM

Humans read “7:45” as seven three-quarter hours; spreadsheets want 7.75. Showing both formats side by side means one calculation serves your wall clock and your invoice template without mental conversion.

Why overnight spans are refused

A start of 22:00 and end of 06:00 could mean eight hours or minus sixteen; the tool cannot know if midnight was crossed, so it asks you to use same-day times instead of guessing wrong. For night shifts, split the entry at midnight into two calculations.

Strict parsing on purpose

Loose parsers silently turn “9:5” into something surprising. Requiring exact HH:MM keeps typos out of timesheets, where small errors compound across a pay period.

How it's calculated

The math behind this calculator

Duration = end − start (minutes), rendered as H:MM:SS Decimal hours = minutes ÷ 60

Both inputs must be strict 24-hour HH:MM strings with two-digit hours and minutes. Each converts to minutes since midnight; the difference becomes an H:MM:SS duration and, divided by sixty, decimal hours; the format payroll and invoicing systems usually expect.

Assumptions & limitations

  • Both times fall on the same calendar day; overnight spans are rejected.
  • 24-hour notation only; “2:45 PM” style input is not accepted.
  • Seconds granularity is not offered; results resolve to whole minutes.

Worked example

From 09:15 to 12:45 is a 3:30:00 shift; 210 minutes or 3.5 decimal hours for a timesheet.

FAQ

Frequently asked questions

Can I calculate overnight durations?
No; both times are treated as same-day. Split a night shift at midnight and add the two results together.
Why was my input rejected?
Times must be strict 24-hour HH:MM with valid ranges (hours 00–23, minutes 00–59) and the end after the start.
How do I convert to billable decimal hours?
The “Decimal hours” row already does it: minutes divided by 60, e.g. 3:30 becomes 3.5.
Does it handle seconds?
Inputs are minute-granular; seconds always render as :00 in the duration.

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