# Hours to Days (h to d)

> Convert hours to days: 1 h = 0.0416667 d. Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.

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

## Formula

- `1 h = 0.0416667 d`
- `days = hours × 0.04166666667`
- Reverse: `hours = days × 24`

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 h = 0.208333 d
- 12.5 h = 0.520833 d
- 100 h = 4.16667 d

## Conversion table

| Hours (h) | Days (d) |
| --- | --- |
| 1 | 0.0416667 |
| 2 | 0.0833333 |
| 3 | 0.125 |
| 4 | 0.166667 |
| 5 | 0.208333 |
| 6 | 0.25 |
| 7 | 0.291667 |
| 8 | 0.333333 |
| 9 | 0.375 |
| 10 | 0.416667 |
| 15 | 0.625 |
| 20 | 0.833333 |
| 25 | 1.04167 |
| 30 | 1.25 |
| 40 | 1.66667 |
| 50 | 2.08333 |
| 75 | 3.125 |
| 100 | 4.16667 |
| 200 | 8.33333 |
| 250 | 10.4167 |
| 500 | 20.8333 |
| 1000 | 41.6667 |

## API

- `GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=h&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":"h","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 hour?**

1 h = 0.0416667 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 hours to days?**

Multiply the value in hours by 0.04166666667: days = hours × 0.04166666667. For example, 5 h = 0.208333 d.

**How do I convert days back to hours?**

Multiply by the inverse factor 24 (hours = days × 24), or use the days-to-hours page.

## Related conversions

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