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Time Calculator

Add, subtract, and calculate time differences with hours, minutes, and seconds

Common Time Examples

Standard Work Day
08:00:00
Half Work Day
04:00:00
Lunch Break
01:00:00
Movie Length
02:30:00
Quick Meeting
00:30:00
Coffee Break
00:15:00

Time Calculator Guide: Add, Subtract, Multiply, Divide & Convert Time

Perform accurate time calculations—including add time, subtract time, time difference, and time to decimal hours—with support for 12-hour/24-hour (military time) and full HH:MM:SS precision. Ideal for timesheets, payroll, project planning, and schedule math across time zones and DST.

Overview

The Time Calculator handles everyday and professional time arithmetic with ease. Add multiple durations, find the time between two times, convert minutes to hours or seconds to hours, and switch between 12-hour and 24-hour formats instantly.

Key Features

Time Operations

  • Addition: Add multiple hours:minutes:seconds values in one go.
  • Subtraction: Compute an exact time difference between two timestamps.
  • Multiplication: Scale a duration by a number (e.g., 2.5 × 1:45:00).
  • Division: Split a duration (e.g., project total / team size) or find averages.

Time Formats & Outputs

  • 12-hour with AM/PM and 24-hour (military time).
  • Decimal hours for billing/payroll (e.g., 8:45 → 8.75).
  • Days, hours, minutes, seconds with optional milliseconds.

How to Use

Basic Time Arithmetic

  1. Enter Time Values in HH:MM or HH:MM:SS.
  2. Choose Operation: add, subtract, multiply, or divide.
  3. Calculate: See results in 12-hour, 24-hour, and decimal hours.

Duration Calculations (Start/End)

  1. Start Time (e.g., 08:30).
  2. End Time (e.g., 17:15).
  3. Breaks (e.g., 00:45).
  4. Result: Net time worked plus decimal for payroll.

Tip: For time zone scenarios (meetings across regions), convert both times into a common time zone first, especially around Daylight Saving Time changes.

Common Use Cases

Work & Payroll

  • Total weekly work hours from daily shifts.
  • Subtract lunch/breaks and round to billing increments.
  • Convert to decimal hours for timesheets and overtime rules.

Project Management

  • Sum task durations and milestones.
  • Calculate ETAs and critical-path buffers.
  • Average task times across contributors.

Personal Time Tracking

  • Exercise and study sessions.
  • Travel time planning and layovers.
  • Event schedules and turnarounds.

Time Conversion Examples

| Input | 12-Hour | 24-Hour | Decimal | |--------------|----------|---------|-------------| | 2:30 PM | 2:30 PM | 14:30 | 14.5 hours | | 8 h 45 min | 8:45 | 08:45 | 8.75 hours | | 90 minutes | 1:30 | 01:30 | 1.5 hours | | 0.25 hours | 15 mins | 00:15 | 0.25 hours |

Formula (time → decimal hours)

decimal_hours = hours + (minutes ÷ 60) + (seconds ÷ 3600)

Tips for Accurate Calculations

Time Entry

  • Use consistent formats (HH:MM or HH:MM:SS).
  • For 12-hour times, confirm AM/PM.
  • Remember: 12:00 AM = 00:00, 12:00 PM = 12:00.

Working with Durations

  • For global schedules, normalize to a shared time zone before calculating.
  • Mind DST transitions—an hour can be skipped (spring) or repeated (autumn).

Rounding & Precision

  • Choose rounding aligned with your policy: nearest minute, 0.1 h, 0.25 h (quarter hour), etc.
  • Use seconds when precision matters (e.g., labs, video, sports).

Advanced Features

Bulk Operations

  • Paste a list of times to add or average.
  • Find max/min durations across entries.

Time Zone Handling

  • Convert local ↔ UTC or between regions for clean time difference math.
  • Note that DST rules vary by country/region and can change over time.

Business Applications

  • Billable hours with different rates per task/client.
  • Employee time across projects with summaries.
  • Export timesheet-ready decimal totals.

Common Time Formats

Standard Formats

  • ISO 8601: 2025-08-18T14:30:00Z (or with offset, e.g., +01:00)
  • 12-hour: 2:30:00 PM
  • 24-hour: 14:30:00
  • Decimal: 14.5

Duration Formats

  • Hours:Minutes: 2:30
  • Hours:Minutes:Seconds: 2:30:45
  • Total Minutes: 150 minutes
  • Decimal Hours: 2.5 hours

Quick FAQs

How do I add times like 1:45:30 + 2:20:45?
Add seconds (carry to minutes), add minutes (carry to hours), then add hours. The calculator automates this and returns HH:MM:SS, 24-hour, and decimal hours.

What’s the difference between a time calculator and a time duration calculator?
A time calculator handles add/subtract/multiply/divide of time values; a duration calculator (or time difference calculator) focuses on the elapsed time between a start and end timestamp.

How do I convert payroll time to decimals (e.g., 8:30)?
Use the formula: 8 + 30/60 = 8.5. Many companies round to 0.1 h or 0.25 h—follow your policy.

Do I need to worry about DST?
Yes—around clock changes, subtracting local timestamps may be off by ±1 hour. Convert both to a common zone (e.g., UTC) first to avoid errors.

Start using the Time Calculator to add and subtract time, compute time differences, and convert to decimal hours—so your payroll, timesheets, and project timelines stay precise.