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Time Calculator

Add & subtract time, find duration between dates, convert formats, calculate work hours and pay.

Starting time
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Operation
Amount to add / subtract
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Result wrapping
Mode
Time to convert
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Time format
Clock in
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Clock out
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Overnight shift?
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Time Math for Work, Billing, and Project Management

Time calculations seem simple until you try to add 3 hours 47 minutes to 1 hour 58 minutes, time math doesn't follow base-10 rules. Hours convert at 60 minutes, minutes at 60 seconds. The correct answer is 5 hours 45 minutes, not 5:105. For hourly workers and freelancers, accurate time calculation directly equals accurate pay. A worker who records 7 hours 45 minutes per day over 5 days has worked 38 hours 45 minutes, 38.75 decimal hours. At $125/hour, that's $4,843.75. Converting time to decimal hours is the critical step many people get wrong, costing real money on invoices. In project management, time tracking reveals where effort actually goes versus where you think it goes. Research shows people estimate task duration at 2-3x reality for unfamiliar work (the planning fallacy). Tracking actual time builds calibration that improves future estimates and reveals hidden inefficiencies.

CalculatorWizard Team Updated: 2026-04-10
Affiliate Recommendation
⭐ Expert Pick
Top Pick

Time Tracking Notebook: Hourly Log

Paper time tracking for freelancers and hourly workers
Dedicated time tracking log book with hourly breakdowns, daily totals, and weekly summaries, perfect for freelancers and contractors who need accurate records for billing.
✓Hourly time log format
✓Daily and weekly total sections
✓Client/project columns
✓52-week coverage
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How Time Math Works

Time arithmetic is base-60 for minutes and seconds (values 0–59) and base-24 or base-12 for hours. Adding 50 minutes to 9:20 produces 10:10, not 9:70, the carry rules are the same as regular addition but with different base boundaries. The most reliable approach converts everything to total seconds, performs the math, then converts back.

Decimal Hours: the Payroll Standard

Decimal hours express any time as a fraction of one hour. Divide minutes by 60: 30 min = 0.50, 45 min = 0.75, 15 min = 0.25. At $20/hr, 8.75 decimal hours pays exactly $175, far simpler than calculating hours and minutes separately.

MinutesDecimalMinutesDecimal
15 min0.250040 min0.6667
20 min0.333345 min0.7500
30 min0.500050 min0.8333

24-Hour vs 12-Hour Format

The 24-hour (military) clock runs from 00:00 to 23:59 with no AM/PM. To convert 24-hr to 12-hr: subtract 12 from any hour over 12, or use 12 for noon and 12 AM for midnight. Hours 1–11 stay the same (AM); 13–23 become 1–11 PM.

24-hour12-hour24-hour12-hour
00:0012:00 AM13:001:00 PM
09:009:00 AM17:305:30 PM
12:0012:00 PM23:5911:59 PM

Time Tracking & Productivity Tools

Amazon's Choice

Time Tracker Cube: 4 Preset Timers

$29.99
★★★★☆ (18,200)

Physical time tracking cube, flip to start tracking time on each project.

View on Amazon →
Best Seller

Freelancer Invoice & Time Log Planner

$14.99
★★★★☆ (9,800)

Track billable hours and generate invoice-ready time summaries.

View on Amazon →
Top Rated

Deep Work: Rules for Focused Success

$14.99
★★★★☆ (48,300)

The definitive guide to maximizing the value of your working hours.

View on Amazon →
Affiliate Recommendation
🚀 Next Step Recommendation
Best Seller

Deep Work: Cal Newport

Get more done in less time with focused work blocks
Influential book arguing 4 hours of deep, uninterrupted work produces more than 8 hours of distracted effort, with a practical time-blocking methodology.
✓Time blocking methodology
✓Deep vs. shallow work framework
✓Focus session strategies
✓Bestselling productivity book
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Frequently Asked Questions

How do I add hours and minutes together?
Use Add & Subtract mode. Enter your starting time in HH:MM:SS, select “Add time,” enter the duration to add, and click Calculate. Carries are handled automatically.
How do I calculate work hours across midnight?
Use Work Hours mode and toggle “Crosses midnight.” Enter clock-in (e.g. 10:00 PM) and clock-out (e.g. 6:30 AM). The overnight flag adds 24 hours to the clock-out before computing the gap.
What is 8 hours 45 minutes as a decimal?
8.75 decimal hours. Formula: 45 ÷ 60 = 0.75, so 8 + 0.75 = 8.75. Use Convert & Decimal mode with “Time → Decimal” to verify instantly.
How do I convert 14:30 to 12-hour format?
Use Convert & Decimal → All Formats. Enter 14 hours, 30 minutes, 0 seconds. The result instantly shows 2:30:00 PM alongside every other format.

💡 Quick Answers

❓ How do I add and subtract time correctly?
Time adds in base-60, not base-10. To add 2 hours 45 min + 1 hour 30 min: add minutes (45+30=75=1 hour 15 min carry), then add hours (2+1+1=4 hours), giving 4 hours 15 minutes. To subtract, borrow from hours when needed: 3 hours 10 min - 1 hour 40 min → 2 hours 70 min - 1 hour 40 min = 1 hour 30 min. Common error: treating 3:30 + 1:45 as 4:75, it's 5:15.
❓ How do I convert hours and minutes to decimal hours for billing?
Divide the minutes by 60. 7 hours 20 minutes = 7 + (20/60) = 7.333 hours. At $100/hour = $733.33 billable. Quick reference: 6 min = 0.1 hr, 15 min = 0.25 hr, 30 min = 0.5 hr, 45 min = 0.75 hr, 54 min = 0.9 hr. Always convert to decimal before multiplying by your hourly rate.
❓ How many hours are in different time periods?
1 day = 24 hours, 1 week = 168 hours, 1 month (average) ≈ 730.5 hours, 1 year = 8,760 hours (8,784 in a leap year). A standard 40-hour work year = 2,080 hours. Dividing your annual salary by 2,080 gives your effective hourly rate, a $65,000 salary equals approximately $31.25/hour, useful context when evaluating how to spend your time.