Free Time Calculator - Add, Subtract & Convert Time
Calculate time duration, add and subtract time values, and convert between 12-hour and 24-hour formats. Perfect for work hours, project planning, time tracking, and scheduling with precision and ease.
Free Time Calculator - Master Time Management & Calculations
Our comprehensive time calculator helps you add, subtract, and convert time values with precision. Whether you're calculating work hours, project durations, time differences, or converting between 12-hour and 24-hour formats, this tool makes time calculations simple and accurate.
Time Calculation Features
- • Add time values - Sum multiple time durations
- • Subtract time values - Find time differences
- • 12-hour & 24-hour formats - Support for both systems
- • Days, hours, minutes, seconds - Complete time units
- • AM/PM support - Accurate 12-hour calculations
- • Real-time results - Instant calculation updates
Common Use Cases
- • Calculate total work hours and overtime
- • Determine project duration and deadlines
- • Find elapsed time between events
- • Convert between time formats (12/24-hour)
- • Plan schedules and time budgets
- • Track billable hours for freelancing
Perfect for business professionals, project managers, freelancers, and anyone who needs precise time calculations for work, study, or personal time management.
Time Calculator Tool
Add and subtract time with precision
How to use the Time Calculator
- • Select whether you want to Add or Subtract time
- • Choose between 12-hour and 24-hour time format
- • Enter values for days, hours, minutes, and seconds
- • See the result update automatically as you adjust inputs
First Time Value
Second Time Value
Calculation Result
Quick Reference Guide
Time Unit Conversions
- • 1 day = 24 hours = 1,440 minutes
- • 1 hour = 60 minutes = 3,600 seconds
- • 1 minute = 60 seconds
- • 1 week = 7 days = 168 hours
- • 1 year ≈ 365.25 days = 8,766 hours
Time Format Examples
- • 1:30 PM = 13:30 (24-hour)
- • 3:45 PM = 15:45 (24-hour)
- • 11:15 PM = 23:15 (24-hour)
- • 8:20 AM = 08:20 (24-hour)
- • 12:00 AM = 00:00 (midnight)
- • 12:00 PM = 12:00 (noon)
Common Time Calculation Examples
Time Duration Addition
- 8 hours + 45 minutes= 8:45:00
- 72 hours= 3 days
- 90 minutes= 1:30:00
Time Difference Calculation
- 9:30 AM - 5:45 PM= 8:15:00
- 11:45 PM - 1:30 AM= 1:45:00
- Monday - Friday= 4 days
Format Conversion
- 1:30 PM= 13:30
- 23:45= 11:45 PM
- 12:00 AM= 00:00
Understanding Time Calculations & Formats
Time Units & Conversions
Understanding how time units relate to each other:
- SecondThe base unit of time in the International System of Units (SI).
- Minute60 seconds. Derived from ancient Babylonian sexagesimal system.
- Hour60 minutes or 3,600 seconds. Divides the day into 24 equal parts.
- Day24 hours or 86,400 seconds. Based on Earth's rotation period.
Time Calculation Methods
Different approaches to time calculations:
- AdditionCombines two time durations, handling carry-over between units automatically.
- SubtractionFinds the difference between times, handling borrowing between units as needed.
- ConversionTransforms time from one unit to another while preserving the same duration.
- Format ChangeConverts between 12-hour (AM/PM) and 24-hour time formats accurately.
Time Calculation Challenges
Special considerations in time calculations:
- Time ZonesDifferent regions have different standard times; calculations may need zone adjustments.
- DSTDaylight Saving Time can create "missing" or "duplicate" hours during transitions.
- Leap YearsFebruary has 29 days in leap years, affecting calculations spanning this period.
- AM/PM12-hour clock formats require special handling for noon and midnight conversions.
Practical Applications
Real-world uses for time calculations:
- Work HoursCalculate total hours worked, overtime, lunch breaks, and shift durations.
- Project PlanningEstimate task durations, deadlines, milestones, and project timelines.
- Travel PlanningCalculate journey times, arrival times, layovers, and time zone differences.
- Billing & InvoicingCalculate billable hours, service durations, consultation time, and rental periods.
12-Hour vs 24-Hour Time Format Guide
12-Hour Format (AM/PM)
Characteristics:
- • Uses AM (ante meridiem) and PM (post meridiem)
- • Hours range from 1-12
- • 12:00 AM = midnight, 12:00 PM = noon
- • Common in US, Canada, Philippines, Australia
- • Used in everyday conversation and casual settings
Common Examples:
24-Hour Format (Military Time)
Characteristics:
- • No AM/PM designation needed
- • Hours range from 00-23
- • 00:00 = midnight, 12:00 = noon
- • Standard in Europe, military, aviation, medicine
- • Eliminates confusion between AM/PM
Common Examples:
Quick Conversion Tips
12-Hour to 24-Hour:
- • AM hours stay the same (except 12 AM = 00)
- • PM hours: add 12 (except 12 PM stays 12)
- • 1:00 PM = 13:00, 11:59 PM = 23:59
- • 12:30 AM = 00:30, 12:30 PM = 12:30
24-Hour to 12-Hour:
- • 00:xx = 12:xx AM (midnight hour)
- • 01-11:xx = same time AM
- • 12:xx = 12:xx PM (noon hour)
- • 13-23:xx = subtract 12, add PM
Time Calculation Tips & Best Practices
Work Hours Calculation
When calculating work hours, don't forget to subtract break times and lunch periods for accurate totals.
Minus 1-hour lunch = 7 hours worked
Overtime Calculation
Calculate overtime by finding hours worked beyond standard work hours (typically 8 hours/day or 40 hours/week).
Overtime = 10.5 - 8 = 2.5 hours
Project Time Estimation
Add buffer time (15-25%) to project estimates to account for unexpected delays and revisions.
With 20% buffer = 9.6 hours
Cross-Day Calculations
When calculating time that spans midnight, remember to account for the date change in your calculations.
Duration = 3 hours (crosses midnight)
Common Mistakes
Avoid confusion between 12 AM (midnight) and 12 PM (noon). Always double-check AM/PM designations.
12:00 PM = noon
Decimal Time
Convert minutes to decimal for easier calculations: 30 minutes = 0.5 hours, 15 minutes = 0.25 hours.
= 8.75 hours in decimal format