Time Calculator
Three time tools in one place: add or subtract hours and minutes from a clock time, measure the duration between two times, and convert between decimal hours and hours-and-minutes.
Summary
How It Works
Clock arithmetic is awkward because time is not decimal — an hour has 60 minutes, so adding 45 minutes to 9:30 does not work like adding ordinary numbers. This page handles the carrying for you. The add/subtract tool shifts a clock time forward or back by any number of hours and minutes and wraps past midnight when it has to. The duration tool measures the gap between two clock times, treating an earlier end time as the next day, which is exactly how night shifts work. The decimal converter bridges the two ways of writing a length of time: 7.75 hours and 7 hours 45 minutes are the same duration, and payroll systems almost always want the decimal form.
Worked Example
Start at 9:15 AM and add 7 hours 45 minutes: 9:15 plus 7 hours is 4:15 PM, plus 45 minutes is 5:00 PM. For a duration, a shift from 10:30 PM to 6:15 AM the next morning runs 1 hour 30 minutes to midnight plus 6 hours 15 minutes after it, giving 7 hours 45 minutes — or 7.75 hours in decimal form, since 45 minutes is 45 ÷ 60 = 0.75 of an hour.
How to Use This Calculator
Pick the tool that matches your question — all three update live as you type. For add/subtract, enter a start time, choose add or subtract, and enter the hours and minutes to shift by. For duration, enter a start and an end time; if the end time is earlier, it is read as the next day, so a night shift needs no extra step. For the decimal converter, type decimal hours to see hours and minutes, or enter hours and minutes to see the decimal equivalent. Reset restores the example values.
Tips and Practical Advice
Decimal hours are the usual source of payroll mistakes: 7 hours 30 minutes is 7.5 hours, not 7.3, and 7 hours 45 minutes is 7.75, not 7.45 — always divide the minutes by 60. When you plan a day, add time in chunks rather than all at once: add the hours first, then the minutes, so you can sanity-check each step against the clock. And for anything that crosses midnight — a flight, a shift, a long drive — write the date next to each time, because the clock alone cannot tell you which day an arrival falls on.
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