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Contract Duration Calculator

Find the exact length of a contract term in years, months, and days from its start and end dates.

Contract term

Example

1 year, 5 months, and 14 days

Based on

Start date
January 1, 2024
End date
June 15, 2025
Counting
Inclusive (start and end included)

From January 1, 2024 to June 15, 2025, the contract term is 1 year, 5 months, and 14 days.

More detail

Total days
532 days
Total weeks
76 weeks

Next step: Contract End Date Calculator

When to use this calculator

Use this calculator when you already know a contract's start and end dates and need its exact term length—to verify a stated term, compare two agreements, or review an existing contract before renewal.

  • Term verification

    Check that a contract's stated term (for example, "12 months") matches its actual start and end dates.

  • Contract comparison

    Compare the exact duration of two contracts with different start and end dates.

  • Legacy contract review

    Find the exact term of an older agreement that only lists start and end dates, not a stated duration.

  • Renewal planning

    Pair with the Contract Renewal Calculator to plan a cancellation or renewal deadline once you know the term.

Inputs

  • Contract start date

    The date the contract term began.

  • Contract end date

    The date the contract term ends or ended.

  • Include start date

    When on, the start date counts as day one of the term. When off, the count begins the following day.

  • Include end date

    When on, the end date counts as the final day of the term. When off, the count stops the day before.

How the calculation works

Enter the contract's start and end dates. The calculator computes the calendar span in years, months, and days using the same engine as the Age Calculator and Date Duration Calculator—just applied to a contract term instead of a birth date or generic date range.

Total days and total weeks are also shown for contracts that specify their term in days or weeks rather than years and months.

The optional "Include start date" and "Include end date" settings control whether each boundary date counts toward the total, matching the Date Duration Calculator's inclusive/exclusive options.

Worked example

Contract start date: 15 January 2023. Contract end date: 20 June 2025.

Duration: 2 years, 5 months, 5 days.

Total days: 887. Total weeks: 126 complete weeks.

If the contract's terms stated a nominal "two and a half year" term, this result confirms it runs slightly longer than a flat 30-month calendar addition would produce, since actual month lengths vary.

Edge cases

  • Include vs exclude boundary dates

    Including both the start and end dates adds two extra days to the total relative to excluding both—matters most when a contract's total-day count is used for a threshold, such as a minimum-term clause.

  • Leap year spans

    A contract term that crosses 29 February gains one extra day compared to an equivalent span in years without a leap day, affecting the total-days figure even when the years/months/days breakdown looks the same.

  • End date before start date

    The end date must fall on or after the start date. Reversed dates do not produce a valid duration.

  • Same-day contracts

    A start and end date on the same day produces a duration of 0 years, 0 months, 0 or 1 days depending on the include-boundary settings—useful as a sanity check before entering real dates.

Related Contracts & Legal Calculators

The Contract End Date Guide is the primary reference for how contract end dates are calculated, how they differ from notice periods, and which calculator to use for each step.

The SLA Deadline Guide covers response and resolution SLA deadlines, business-day vs hour-based clocks, and holiday handling for helpdesk and vendor agreements.

The Contract End Date Calculator projects a contract end date from a start date and term length, with 30-, 60-, and 90-day renewal reminder dates.

The Contract Expiry Calculator is the same date math, framed for the 'expiry date' language some contracts, licenses, and subscriptions use instead of 'end date.'

The Contract Duration Calculator works the other way: given a contract's start and end dates, it finds the exact term length in years, months, and days.

The Contract Renewal Calculator works backward from a known end date and a renewal or cancellation notice period, to find the deadline to act before auto-renewal.

The License Renewal Calculator and Certification Renewal Calculator apply the same issue-date-plus-validity-period math to licenses, permits, and professional credentials rather than contracts.

The SLA Deadline Calculator adds hours, calendar days, or business days to a start date and time to produce a response or resolution deadline in UTC.

For notice periods tied to an employment relationship rather than a contract or vendor agreement, see the Notice Period Calculator in HR & Employment.

For business-day counting that contract and SLA deadlines depend on, see the Business Days Calculator and Add Business Days To Date Calculator in Date & Business Days.

FAQ

How do I calculate a contract's duration?
Enter the contract's start date and end date. The calculator shows the duration in years, months, and days, plus total days and weeks.
How is this different from the Date Duration Calculator?
Same underlying date-span engine—no new math—framed for contract terms: a contract start and end date instead of generic start and end dates.
How is this different from the Contract End Date Calculator?
The Contract End Date Calculator goes forward: start date plus a stated term gives you the end date. This calculator goes the other way: given both dates already, it tells you the exact term length.
Which include/exclude setting should I use?
Match your contract's own wording. Most commercial contracts count both the start and end date as part of the term, but some agreements define the term as starting the day after signing—check the specific clause.

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