Time Calculator — Add & Subtract Time or Fill a Time Card

Quick Start Guide

  1. Add time entries: Enter hours, minutes, and seconds.
  2. Choose operation: Set + or - for each row.
  3. Review total: See the combined duration instantly.

Understanding Time Math

How entries combine

Every entry is converted to total seconds (hours × 3600 + minutes × 60 + seconds), then added or subtracted according to its +/- operator. The running total is only converted back to hours/minutes/seconds for display at the end, so there's no manual carrying to get wrong.

Negative totals

If subtracted entries outweigh added ones, the total is negative and displayed with a leading minus sign (e.g. -01:00:00) rather than wrapping or erroring.

Decimal hours and workdays

Decimal Hours (e.g. 15.08 instead of 15:05) is the format most payroll and timesheet tools expect. 8h Workdays divides the total by a standard 8-hour day, useful for estimating how many working days a total represents.

What this calculator does not cover

This adds and subtracts durations — it does not compute elapsed time between two clock times or convert between time zones. For clock-time and time zone conversions, see the Date Difference and Time Zone calculators.

Features

Time Card Mode: Clock-in and clock-out per shift with unpaid breaks, an optional day label, and per-shift worked time — totalled in H:MM:SS and payroll decimal hours.

Decimal Entries: 4.98 hours means 4.98 hours — fractional hours, minutes and seconds all count exactly.

Multiple Rows: Combine many durations in one calculation.

Auto Formatting: Readable time formatting with normalized units.

Add/Subtract: Flexible time arithmetic for real workflows.

Realtime Updates: Results refresh as values change.

Export: Save time calculations to JSON/CSV/PDF.

Common Use Cases

Timesheets & time cards: total daily/weekly work durations and prepare time card, reporting, and billing logs.

Project Management: combine task durations into project totals and compare actual time vs estimates.

Time Arithmetic: add/subtract mixed durations and convert between hours, minutes, and seconds naturally.

Client Billing: calculate billable totals by activity and export records for invoicing.

Frequently Asked Questions

Switch the Mode toggle to Time Card. Each shift row takes a clock-in, a clock-out, an unpaid break in minutes, and an optional day label; the worked time for that row shows as you type, and the panel totals every shift in hours:minutes and in payroll decimal hours. A clock-out earlier than the clock-in is treated as an overnight shift — 22:00 to 06:00 is eight hours.
Decimal hours express minutes as hundredths of an hour, so 7:30 is 7.50 hours — the form payroll systems multiply by an hourly rate. The results panel shows the total both ways, and you can also type decimal values directly: subtracting 4.98 hours really subtracts 4.98 hours, not 4.
Add seconds, minutes, and hours separately. If seconds > 59, subtract 60 and add 1 minute. Do the same for minutes. Our calculator handles this carry-over automatically.
Add a duration entry and set its operator to "-" instead of "+". If subtracted entries outweigh added ones, the total displays as negative (e.g., -01:00:00) rather than wrapping — useful for tracking overtime or deducting breaks from worked hours.
Yes. For example, 1 hour 30 minutes = 1.5 hours (divide minutes by 60 and add to hours). The Decimal Hours figure in the results panel converts your total automatically, which is useful for payroll and billing calculations.
Yes. Export your time calculations to JSON, CSV, or PDF format. This is perfect for time tracking, billing, or creating time reports. The export includes all entries and the calculated total time.

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