# Years (365 days) to Weeks (yr to wk)

> Convert years (365 days) to weeks: 1 yr = 52.1429 wk. Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.

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

## Formula

- `1 yr = 52.1429 wk`
- `weeks = years (365 days) × 52.14285714`
- Reverse: `years (365 days) = weeks × 0.01917808219`

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 = 260.714 wk
- 12.5 yr = 651.786 wk
- 100 yr = 5214.29 wk

## Conversion table

| Years (365 days) (yr) | Weeks (wk) |
| --- | --- |
| 1 | 52.1429 |
| 2 | 104.286 |
| 3 | 156.429 |
| 4 | 208.571 |
| 5 | 260.714 |
| 6 | 312.857 |
| 7 | 365 |
| 8 | 417.143 |
| 9 | 469.286 |
| 10 | 521.429 |
| 15 | 782.143 |
| 20 | 1042.86 |
| 25 | 1303.57 |
| 30 | 1564.29 |
| 40 | 2085.71 |
| 50 | 2607.14 |
| 75 | 3910.71 |
| 100 | 5214.29 |
| 200 | 10428.6 |
| 250 | 13035.7 |
| 500 | 26071.4 |
| 1000 | 52142.9 |

## API

- `GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=year_365&to_unit=week` → 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":"week"}`
- 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 weeks are in one year?**

1 yr = 52.1429 wk. 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 weeks?**

Multiply the value in years (365 days) by 52.14285714: weeks = years (365 days) × 52.14285714. For example, 5 yr = 260.714 wk.

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

Multiply by the inverse factor 0.01917808219 (years (365 days) = weeks × 0.01917808219), or use the weeks-to-years (365 days) page.

## Related conversions

- [Weeks to years (365 days)](https://tttkmbb.com/conversion/weeks-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)