YEARFRAC()
Calculates the fraction of a year between two dates, using a chosen day-count basis.
YEARFRAC(start_date, end_date, [basis])YEARFRAC returns the number of years, expressed as a decimal fraction, between two dates. It's commonly used for prorating annual figures like interest, depreciation, or subscription fees over a partial year.
The basis argument controls how days are counted: 0 (default) uses the US 30/360 convention where every month is treated as 30 days; 1 uses actual calendar days over the actual number of days in the relevant year(s); 2 uses actual days over a 360-day year; 3 uses actual days over a fixed 365-day year; and 4 uses the European 30/360 convention.
Different basis values can give noticeably different answers for the same two dates, especially across a leap year, so it's worth confirming which basis matches the day-count convention used by whatever contract or financial model the formula supports.
Arguments
- start_date
- The starting date.
- end_date
- The ending date.
- basisoptional
- The day-count basis: 0 = US 30/360 (default), 1 = actual/actual, 2 = actual/360, 3 = actual/365, 4 = European 30/360.
Examples
=YEARFRAC(DATE(2024,1,1), DATE(2024,7,1))Exactly half a year under the default 30/360 basis.
=YEARFRAC(DATE(2024,1,1), DATE(2024,7,1), 3)The actual/365 basis counts the true 182 calendar days between the dates, giving a slightly different result than the default basis.
YEARFRAC tricks, tips, and workbook hacks
YEARFRAC is easier to remember when you learn the small patterns around it: where it fits, what can break it, and how to combine it with neighboring functions.
Use these practical notes as a working checklist before putting the formula into a real report, model, dashboard, tracker, or reusable template.
Quick wins before you trust the result
- Start with the simplest YEARFRAC formula that answers the question, then add conditions or error handling only when needed.
- Keep input ranges consistent in size, shape, and meaning.
- Test the formula on one row or one small sample before filling it down a large workbook.
- Add a note beside important formulas explaining what business question they answer.
- Pair the formula with related checks so mistakes are easier to spot.
| Trick or hack | Formula pattern | Best use | Watch out |
|---|---|---|---|
| Build the formula in layers | YEARFRAC(start_date, end_date, [basis]) | When the full formula feels hard to read or debug. | Confirm each argument or nested function before combining everything. |
| Use structured references | =YEARFRAC(Table1[Column]) | Excel Tables make formulas easier to read and expand automatically. | Rename table columns carefully so formulas remain clear. |
| Protect against bad input | =IFERROR(YEARFRAC(...),"Check input") | Dashboards and shared templates where users need a readable message. | Do not hide errors until you understand why they happen. |
| Document the expected result | Add a note or nearby label | Reusable workbooks, finance models, templates, and handoff files. | A clever formula without context becomes expensive to maintain. |
| Mistake | What it looks like | Fix |
|---|---|---|
| Using a wider range than intended | The result changes unexpectedly after new rows or helper columns are added. | Use Excel Tables or named ranges to make the intended input explicit. |
| Mixing text, numbers, dates, and blanks | The answer technically works but does not match the business meaning. | Clean and validate the source column before applying the function. |
| Copying a formula with moving references | The first row works; later rows drift into the wrong range. | Use absolute references, structured references, or named ranges where needed. |
| Scenario | Use | Avoid |
|---|---|---|
| You need a quick answer from clean data | YEARFRAC with the smallest clear range | Overbuilding the formula with unnecessary wrappers |
| The result will appear in a dashboard | Add checks, labels, and readable fallbacks | Leaving raw errors or unexplained blanks for viewers |
| The workbook will grow over time | Excel Tables, named ranges, or structured references | Hard-coded ranges that miss new rows |
| The data comes from another system | Clean inputs before summarizing or transforming | Assuming pasted data has correct types and spacing |
Practice drills
- Write YEARFRAC once with direct cell references and once with an Excel Table reference.
- Break the formula on purpose, then use the error message to identify which argument failed.
- Create a small before/after example that explains the formula to another learner.
