Hours Calculator
An hours calculator adds work hours, converts them to decimal hours, and multiplies by an hourly rate to find pay. A 40-hour week at $25 an hour is $1,000, and a 37.5-hour week at the same rate is $937.50. The time calculator above totals a week from daily start and end times, subtracts the daily break, and shows the pay, and this page explains the hours arithmetic, the decimal conversion, and the overtime rule.
Hours are the unit of paid work, and the arithmetic that matters is the conversion between hours-and-minutes and decimal hours. Seven hours 30 minutes is 7.50 decimal hours, not 7.30, and the difference is 12 minutes of pay per hour of error. This page works through weekly totals, shows the pay calculation at several rates, and explains how overtime is usually counted on top of the first 40 hours.
Add or subtract durations
Time between two clock times
Weekly timesheet: Monday to Friday
How Time Arithmetic Works: Adding, Subtracting, and Pay
Time arithmetic is base-60 arithmetic, which is why it feels unfamiliar: 60 minutes make an hour, so 2 hours 45 minutes plus 1 hour 30 minutes is 4 hours 15 minutes, not 3 hours 75 minutes, because the 75 minutes carry one hour. The reliable method is to convert everything to minutes, add or subtract, and convert back: 165 + 90 = 255 minutes, and 255 ÷ 60 = 4 hours with 15 minutes left over. The calculator above does this conversion for you, and it also converts the result to decimal hours, so 7 hours 30 minutes is 7.50 hours for pay and billing.
The time between two clock times is a subtraction with the same carry rule. From 9:00 AM to 5:00 PM is 8 hours, and with a 30-minute break the working time is 7 hours 30 minutes. Overnight spans need one extra step: from 10:00 PM to 6:00 AM is 8 hours, because the clock passes midnight, so the end time belongs to the next day. A five-day week of 9:00 AM to 5:00 PM with a 30-minute break each day totals 37 hours 30 minutes, which is 37.50 decimal hours, and at $25 an hour that is $937.50 of pay.
The United States time standards behind these calculations are maintained by the National Institute of Standards and Technology, whose time and frequency work is published at nist.gov. The arithmetic on this page is the same base-60 arithmetic that clocks, timesheets, and payroll systems all use.
Step 1 — Convert Every Duration to Minutes
Multiply the hours by 60 and add the minutes: 2 hours 45 minutes is 165 minutes, and 1 hour 30 minutes is 90 minutes. Working in minutes removes the base-60 confusion entirely, and it is the step the calculator performs internally.
Step 2 — Add or Subtract the Minutes
Add the minute totals: 165 + 90 = 255 minutes. For a time between two clock times, subtract the start minutes from the end minutes, adding 1,440 minutes (24 hours) to the end first if the span crosses midnight.
Step 3 — Convert Back to Hours and Minutes
Divide by 60: 255 ÷ 60 = 4 hours with 15 minutes left over, so the answer is 4 hours 15 minutes. For pay, divide the total minutes by 60 to get decimal hours: 450 minutes is 7.50 hours, and 7.50 × $25 = $937.50.
Worked Examples: Hours and Pay
Each row gives a weekly pattern, the decimal hours, and the pay at the stated rate, with the arithmetic shown.
| Weekly pattern | Hours | Pay |
|---|---|---|
| 40 hours at $25 per hour | 40.00 | $1,000.00 |
| 37.5 hours at $25 per hour | 37.50 | $937.50 |
| 45 hours at $20 per hour | 45.00 | $900.00 |
| 30 hours at $30 per hour | 30.00 | $900.00 |
| 8 hours a day, 5 days, at $25 per hour | 40.00 | $1,000.00 |
The second row is the five-day 9:00 AM to 5:00 PM pattern with a 30-minute break: each day is 7 hours 30 minutes, five days is 37 hours 30 minutes, which is 37.50 decimal hours, and 37.50 × $25 = $937.50. The third row is the overtime case: 45 hours at $20 is $900.00 at the straight rate, but under the common overtime rule the 5 hours over 40 are paid at time and a half, which is $30 an hour, giving 40 × $20 + 5 × $30 = $800 + $150 = $950.00. Check your own contract for the overtime rule that applies to you.
How to Use the Time Calculator
The calculator has modes for adding and subtracting durations, for the time between two clock times, and for a full weekly timesheet with daily breaks and an hourly rate. Enter your times and it shows hours, minutes, decimal hours, and pay.
- Choose the mode. Add durations for totals, between two times for a single span, or timesheet for a full week with a break each day.
- Enter the hours and minutes. The default durations add to a clean example; change any field and the total updates immediately.
- Set the break for timesheet mode. The default 30-minute daily break is subtracted from each day before the weekly total is computed.
- Enter an hourly rate to see pay. The calculator multiplies decimal hours by your rate, so 37.50 hours at $25 an hour shows $937.50.
- Read the decimal hours. Payroll and billing use decimal hours, so 7 hours 30 minutes is 7.50 hours, not 7.30, and the calculator shows both forms.
Hours, Decimal Hours, and Pay at $25 an Hour
This table converts common weekly totals into decimal hours and pay at $25 an hour, the rate used in the examples.
| Weekly total | Decimal hours | Pay at $25/hour |
|---|---|---|
| 35 hours | 35.00 | $875.00 |
| 37 hours 30 minutes | 37.50 | $937.50 |
| 40 hours | 40.00 | $1,000.00 |
| 45 hours | 45.00 | $1,125.00 |
| 50 hours | 50.00 | $1,250.00 |
Common Mistakes With Time Arithmetic
Time is the only everyday arithmetic that runs in base 60, and that is exactly where the mistakes come from.
- Writing 7.30 for 7 hours 30 minutes. In decimal hours, 30 minutes is 0.50, not 0.30, so 7 hours 30 minutes is 7.50 hours. The .30 error underpays by 12 minutes an hour.
- Forgetting to carry 60 minutes. 2 hours 45 minutes plus 1 hour 30 minutes is 4 hours 15 minutes, not 3 hours 75 minutes, because 75 minutes carries an hour.
- Forgetting midnight. A shift from 10:00 PM to 6:00 AM is 8 hours, not negative 16, because the end time belongs to the next day.
- Subtracting the break twice. A 30-minute break is subtracted once per day; subtracting it from the total as well as from each day double-counts it.
- Mixing 12-hour and 24-hour times. 5:00 PM is 17:00, and subtracting 9:00 from 5:00 without the PM gives a wrong or negative answer.
Where You Will Use Time Arithmetic
Adding hours, measuring spans, and totalling timesheets are the arithmetic of work, travel, and everyday planning.
- Timesheets and payroll. A week of 9:00 AM to 5:00 PM with a 30-minute break is 37 hours 30 minutes, and the pay follows from the decimal hours.
- Shift planning. The gap between a shift’s start and end, minus breaks, is the paid time, and it must be right before the roster is published.
- Travel. The time between departure and arrival, across time zones and overnight, is the journey length, and it decides connections and rest.
- Project tracking. Adding task durations in hours and minutes shows the total effort, and converting to decimal hours prices it.
- Daily routines. Adding a workout, a commute, and a lunch break shows how much of the day is spoken for, and how much is left.
Overtime: The 40-Hour Line
In the United States, the Fair Labor Standards Act requires overtime pay of at least time and a half for hours over 40 in a workweek, for non-exempt employees. The 45-hour week at $20 an hour is therefore $800.00 for the first 40 hours plus $150.00 for the 5 overtime hours at $30 an hour, which is $950.00 in total, not the $900.00 the straight rate gives. State laws can add daily overtime or a higher threshold, and salaried or exempt roles follow different rules, so the calculator’s pay figure is an estimate and the contract and the law decide the actual pay.
Tips for Accurate Results
Time arithmetic rewards a steady method. These habits keep the minutes honest.
- Always work in minutes. Convert to minutes, do the arithmetic, and convert back; it removes the base-60 confusion at a stroke.
- Write AM and PM explicitly. A 12-hour time without AM or PM is ambiguous, and the ambiguity always costs an hour or twelve.
- Record the break once per day. In a timesheet, the break belongs to the day it was taken, not to the weekly total.
- Use decimal hours for money. Multiply decimal hours by the rate, never hours-and-minutes notation, or the pay will be wrong.
- Check overnight spans by adding. From 10:00 PM, add the hours forward past midnight to 6:00 AM and count: 2 hours to midnight plus 6 hours is 8.
Time Quick Answers
These are the time answers people look up most often, each one verified against the calculator above.
| Question | Answer |
|---|---|
| 2 hours 45 minutes + 1 hour 30 minutes | 4 hours 15 minutes |
| 9:00 AM to 5:00 PM, less a 30-minute break | 7 hours 30 minutes |
| 37.50 hours at $25 an hour | $937.50 |
| 40 hours at $25 an hour | $1,000.00 |
| 10:00 PM to 6:00 AM | 8 hours |
Related tools on this site: the main time calculator, salary calculator, days calculator, percentage calculator, and the time calculator again whenever you need a fresh check.
Frequently Asked Questions
How many hours are in a 40-hour work week?
There are 40 hours: 8 hours a day for 5 days, or any other pattern that totals 40. A 9:00 AM to 5:00 PM week with a 30-minute break each day is 37 hours 30 minutes, not 40, because the break is unpaid time.
How do I calculate pay from hours and rate?
Convert the hours to decimal hours, then multiply by the hourly rate. For 37.50 hours at $25 an hour, the pay is 37.50 × $25 = $937.50. For 40 hours at the same rate, it is 40 × $25 = $1,000.00.
What is 37.5 hours in hours and minutes?
It is 37 hours 30 minutes, because 0.50 of an hour is 30 minutes. The decimal .50 is half an hour, not 50 minutes, which is the conversion most people get wrong.
How is overtime calculated?
Under the Fair Labor Standards Act, non-exempt employees earn at least time and a half for hours over 40 in a workweek. A 45-hour week at $20 an hour is 40 × $20 + 5 × $30 = $950.00.
How do I add hours across a week?
Add the daily durations in minutes, then convert back: five days of 7 hours 30 minutes is 5 × 450 = 2,250 minutes, which is 37 hours 30 minutes, or 37.50 decimal hours. The calculator above totals the week from the daily times.
Disclaimer: This calculator is for general information only. Pay figures are estimates from the hours and rate you enter; actual pay is governed by your employer, your contract, and applicable labour law, including overtime rules.