# Days to Months (30 days) (d to mo)

> Convert days to months (30 days): 1 d = 0.0333333 mo. Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.

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

## Formula

- `1 d = 0.0333333 mo`
- `months (30 days) = days × 0.03333333333`
- Reverse: `days = months (30 days) × 30`

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 d = 0.166667 mo
- 12.5 d = 0.416667 mo
- 100 d = 3.33333 mo

## Conversion table

| Days (d) | Months (30 days) (mo) |
| --- | --- |
| 1 | 0.0333333 |
| 2 | 0.0666667 |
| 3 | 0.1 |
| 4 | 0.133333 |
| 5 | 0.166667 |
| 6 | 0.2 |
| 7 | 0.233333 |
| 8 | 0.266667 |
| 9 | 0.3 |
| 10 | 0.333333 |
| 15 | 0.5 |
| 20 | 0.666667 |
| 25 | 0.833333 |
| 30 | 1 |
| 40 | 1.33333 |
| 50 | 1.66667 |
| 75 | 2.5 |
| 100 | 3.33333 |
| 200 | 6.66667 |
| 250 | 8.33333 |
| 500 | 16.6667 |
| 1000 | 33.3333 |

## API

- `GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=day&to_unit=month_30` → 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":"day","to_unit":"month_30"}`
- 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 months (30 days) are in one day?**

1 d = 0.0333333 mo. 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 days to months (30 days)?**

Multiply the value in days by 0.03333333333: months (30 days) = days × 0.03333333333. For example, 5 d = 0.166667 mo.

**How do I convert months (30 days) back to days?**

Multiply by the inverse factor 30 (days = months (30 days) × 30), or use the months (30 days)-to-days page.

## Related conversions

- [Months (30 days) to days](https://tttkmbb.com/conversion/months-to-days.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)