Convert between milliseconds, seconds, minutes, hours, days, weeks, months, and years.
How the Time Conversion Calculator Works
This calculator converts a value between time units by first converting your input into seconds — the common base unit — and then converting that number of seconds into your target unit. It supports milliseconds, seconds, minutes, hours, days, weeks, average months, and average years, and also displays your value converted into every supported unit at once.
Converted Value = Input Value × (Seconds per From-Unit) ÷ (Seconds per To-Unit)
Why "Average" Month and Year?
Calendar months and years don't have a single fixed length — months range from 28 to 31 days, and years vary between 365 and 366 days for leap years. This calculator uses standard average values: a month is treated as 30.44 days (365.25 ÷ 12) and a year as 365.25 days, which accounts for the leap-year cycle. These averaged values are the standard approach used for general-purpose time unit conversions.
Common Time Conversion Uses
This tool is useful for quickly converting between units in everyday contexts — translating a project timeline from weeks into days, converting a duration in minutes into hours for a timesheet, or understanding how many seconds are in a given number of days for a countdown or scheduling calculation.
❓ Frequently Asked Questions
Why does a 'month' use 30.44 days instead of an exact 30 or 31 days? ▼
Since real calendar months vary in length (28 to 31 days), this calculator uses the standard average month length of 30.44 days (365.25 ÷ 12), giving a consistent, defensible conversion factor rather than picking one arbitrary month length.
Why does this calculator use 365.25 days for a year instead of 365? ▼
365.25 days accounts for the leap-year cycle (an extra day every 4 years), giving a more accurate long-term average year length than a flat 365 days, which is the standard convention for generic year-to-other-unit conversions.
Can I convert directly between any two of the supported units? ▼
Yes. All conversions route through seconds as the base unit, so you can convert directly between any pair — for example, weeks to minutes, or milliseconds to years — by selecting your From and To units.
Why does the calculator show a full table of all units at once? ▼
The all-units table lets you see your entered value's equivalent across every supported time unit in a single glance, which is useful when you're not sure which specific unit you need for comparison.
Is this calculator precise enough for scientific or engineering use? ▼
For everyday conversions it's accurate and uses standard time-unit definitions. For precision timekeeping applications (e.g., accounting for leap seconds or exact calendar dates), specialized timekeeping tools are more appropriate than average-based month/year conversions.
🏆 About This Tool — Accuracy & Trust
🔒 Data Privacy: All calculations run entirely within your browser using JavaScript. Nothing you enter here is ever transmitted to our servers, stored, sold, or shared.
📐 Accuracy Note: This tool uses standard, widely published formulas and guidelines. Results are estimates for informational purposes; for financial, medical, or engineering decisions, consult a licensed professional.
📅 Last Updated: September 2026.