# Years (365 days) to Days (yr to d)

> Convert years (365 days) to days: 1 yr = 365 d. Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.

- Page id: `years-to-days` · Quantity: Time (`time`, base unit s) · Tool: `convert_units`
- Canonical page: https://tttkmbb.com/conversion/years-to-days · This document: https://tttkmbb.com/conversion/years-to-days.md · JSON: https://tttkmbb.com/conversion/years-to-days.json (add `?value=` for a result)

## Formula

- `1 yr = 365 d`
- `days = years (365 days) × 365`
- Reverse: `years (365 days) = days × 0.002739726027`

The factor follows from the SI definitions of both units (NIST SP 811); values below are rounded to 6 significant figures, the API returns up to 12.

## Worked examples

- 5 yr = 1825 d
- 12.5 yr = 4562.5 d
- 100 yr = 36500 d

## Conversion table

| Years (365 days) (yr) | Days (d) |
| --- | --- |
| 1 | 365 |
| 2 | 730 |
| 3 | 1095 |
| 4 | 1460 |
| 5 | 1825 |
| 6 | 2190 |
| 7 | 2555 |
| 8 | 2920 |
| 9 | 3285 |
| 10 | 3650 |
| 15 | 5475 |
| 20 | 7300 |
| 25 | 9125 |
| 30 | 10950 |
| 40 | 14600 |
| 50 | 18250 |
| 75 | 27375 |
| 100 | 36500 |
| 200 | 73000 |
| 250 | 91250 |
| 500 | 182500 |
| 1000 | 365000 |

## API

- `GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=year_365&to_unit=day` → unified JSON envelope with `result.values.result`, `formula`, `factor`, `sources`, `freshness`
- MCP: server `https://tttkmbb.com/mcp`, tool `convert_units` with `{"value":5,"from_unit":"year_365","to_unit":"day"}`
- All time units: https://tttkmbb.com/api/v1/units?quantity=time · full converter: [Time Converter](https://tttkmbb.com/conversion/time.md)
- Authentication: none. Freshness: `static` (fixed conversion factors).

## FAQ

**How many days are in one year?**

1 yr = 365 d. The factor comes from the SI definitions of both units (NIST SP 811 / BIPM), so it is exact or correct to at least 10 significant figures.

**What is the formula to convert years (365 days) to days?**

Multiply the value in years (365 days) by 365: days = years (365 days) × 365. For example, 5 yr = 1825 d.

**How do I convert days back to years (365 days)?**

Multiply by the inverse factor 0.002739726027 (years (365 days) = days × 0.002739726027), or use the days-to-years (365 days) page.

## Related conversions

- [Days to years (365 days)](https://tttkmbb.com/conversion/days-to-years.md) (reverse)
- [Hours to Minutes](https://tttkmbb.com/conversion/hours-to-minutes.md)
- [Minutes to Hours](https://tttkmbb.com/conversion/minutes-to-hours.md)
- [Minutes to Seconds](https://tttkmbb.com/conversion/minutes-to-seconds.md)
- [Seconds to Minutes](https://tttkmbb.com/conversion/seconds-to-minutes.md)
- [Days to Hours](https://tttkmbb.com/conversion/days-to-hours.md)
- [Hours to Days](https://tttkmbb.com/conversion/hours-to-days.md)
- [Weeks to Days](https://tttkmbb.com/conversion/weeks-to-days.md)
- [Days to Weeks](https://tttkmbb.com/conversion/days-to-weeks.md)

## Data Sources

- NIST Special Publication 811 – Guide for the Use of the International System of Units (SI), Appendix B conversion factors — https://www.nist.gov/pml/special-publication-811 (standard, retrieved 2026-09-24)
- BIPM – The International System of Units (SI Brochure, 9th edition) — https://www.bipm.org/en/publications/si-brochure (standard, retrieved 2026-09-24)
- Wikipedia – Conversion of units — https://en.wikipedia.org/wiki/Conversion_of_units (reference, retrieved 2026-09-24)