Conversions

Time Unit Converter

What this does

Convert durations among milliseconds, seconds, minutes, hours, days, weeks, months and years with calendar-average definitions.

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Runs in your browser

Calculator inputs

How to use it

Using the time unit converter

  1. 01

    Enter the duration

    Decimals allowed; 1.5 weeks is fine.

  2. 02

    Choose the units

    From milliseconds for code timeouts to years for amortization schedules.

  3. 03

    Read the breakdown

    Context rows translate the same duration into weeks, days and hours.

Good to know

Why 30.44 days?

Calendar months run 28–31 days, so converters use the Gregorian-year average: 365.25 ÷ 12 ≈ 30.44. For billing-grade precision across specific dates use a date-difference tool instead; this one answers on-average questions.

The leap-day footnote

Leap years add a day roughly every four years; averaging over 365.25-day years absorbs that drift. Leap seconds exist too but are far too small to register at human-scale durations.

Where milliseconds matter

Developers live in ms: API timeouts, animation frames (16.67 ms at 60 fps), database query budgets. The converter bridges that world to the weeks-and-quarters language of planning meetings.

How it's calculated

The math behind this calculator

result = value × factor(from) ÷ factor(to) month = 30.44 days (365.25 ÷ 12) year = 365.25 days

Durations reduce to seconds using fixed averages: months are 30.44 days (365.25 ÷ 12, smoothing leap years) and years are 365.25 days (the Julian average). This keeps month-to-week conversions consistent year-round instead of depending on which months you span.

Assumptions & limitations

  • Results are rounded only for display; full precision is used internally.
  • Conversions use exact standard definitions of each unit.

Worked example

A 30-year mortgage term spans about 10,958 days of interest accrual.

FAQ

Frequently asked questions

How many weeks are in a year?
52 weeks plus one day (two in leap years); the 365.25-day average works out to about 52.18 weeks.
Why is a month not 30 days here?
Because twelve 30-day months would lose more than five days a year. The 30.44-day average reconciles months with the solar year.
Does this handle business days?
No; weekends and holidays are calendar-specific. Use a working-days calculator for payroll-style spans.

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