Math & Science Tools
Free online calculators for everyday math, time math, measurements and precision-focused calculations. Choose a tool below to calculate elapsed time, add or subtract clock values, or work with significant figures.
Significant Figures Calculator
Count significant figures, round measured values, and apply precision rules to addition, subtraction, multiplication and division.
Open calculatorTime Calculator
Do time math: calculate the time difference between two clock times, or add and subtract hours, minutes and seconds.
Open calculatorBusiness Hours Calculator
Calculate business hours across dates with custom work schedules and holidays, or add and subtract working time to find a deadline.
Open calculatorTime Math, Significant Figures and Business Hours
Different calculations need different rules. Use the Time Calculator for ordinary clock-time arithmetic, the Business Hours Calculator when work schedules and holidays matter, and the Significant Figures Calculator when the precision of measured numbers matters.
Time difference and time math
Find elapsed time between a start and end clock time, including an interval that crosses midnight. You can also add or subtract hours, minutes and seconds. For example, 9:30 AM to 5:15 PM is 7 hours 45 minutes, or 7.75 decimal hours.
Business hours and deadlines
Count only the working time inside a configured weekly schedule, exclude entered holidays, or move a deadline forward or backward by business hours. This is different from ordinary elapsed-time math.
Significant figures and arithmetic
Count meaningful digits, round a value, or calculate with measurement precision. For addition and subtraction, use the least precise decimal place; for multiplication and division, use the fewest significant figures.
Math & Science Calculator FAQs
How do I calculate the time difference between two times?
Enter the start and end clock times in the Time Calculator. If the interval ends after midnight, enable its next-day option.
What is the difference between a time calculator and a business hours calculator?
A time calculator handles ordinary clock-time arithmetic and elapsed time. A business-hours calculator counts only the work periods in your configured schedule and can exclude holidays.
How do I add or subtract time?
Use the Time Calculator's Add / Subtract mode and enter hours, minutes and seconds. Minutes are base 60, so 2 hours 30 minutes equals 2.5 hours, not 2.30 hours.
How do significant figures affect addition and subtraction?
For addition and subtraction, round the result to the least precise decimal place in the inputs. For multiplication and division, round to the fewest significant figures in the inputs.