# How do I convert hours to days?

Converts hours (h) to days (d) and back, with the exact unit definitions.

- Page: https://www.acalculator.org/convert/hours-to-days
- JSON spec: https://www.acalculator.org/convert/hours-to-days.json
- Version: b62212728db9

## Default answer

Example with the default inputs (Hours (h) 1): 1 h = 0.041667 d (0 d 1 h).

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| value | Hours (h) | The amount in hours to convert. |
| result | Days (d) | The same amount in days. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| value | Hours (h) | The amount in hours to convert. |
| result | Days (d) | The amount in days. |
| hm | Days and hours | Whole days and the hours left over, to 0.01 h. |

## Method

d = h × 0.0416666666667 (the same as h ÷ 24)

## Assumptions

- 1 hour = 0.0416666666667 days, from the exact definitions in NIST SP 811.
- Exact on the typed decimals: at most 6 decimal places (6 significant digits below 0.0001), rounded half up.
- Days and hours use the box you typed; hours round half up to 0.01, and 24.00 carries.

## Worked examples

1. value = 24 gives result = 1. Source: Exact unit definitions in NIST SP 811 (2008), Appendix B.8.
2. value = 36 gives result = 1.5. Source: Exact unit definitions in NIST SP 811 (2008), Appendix B.8.
3. result = 1.5 gives value = 36. Source: Exact unit definitions in NIST SP 811 (2008), Appendix B.8.

## FAQ

### How many days are in a hour?

1 hour is 0.041667 days, from the exact unit definitions (NIST SP 811).

### How do I convert hours to days?

Multiply by 0.041667: d = h × 0.0416666666667 (the same as h ÷ 24). For example, 1 h × 0.041667 = 0.041667 d.

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

Multiply by 24, or type the days into the second box and the converter works it out. 1 day is 24 hours.

### How many days is 100 hours?

100 ÷ 24 = 4.166667 days, which is 4 whole days and 4 hours.

### How many hours are in a week?

168: 7 days × 24 hours. 168 hours in the converter gives 7 days.

### Does a day always have 24 hours?

Here it does: a day is 86,400 seconds, 24 hours (NIST SP 811). A clock day with a daylight saving change has 23 or 25 hours, which this converter does not count.

## Sources

- NIST SP 811 (2008), Guide for the Use of the International System of Units, Table 5 (SI prefixes) and Appendix B.8 (factors for units listed alphabetically), retrieved 2026-10-05. https://www.nist.gov/pml/special-publication-811