# How do I convert fps to mph?

Converts feet per second (ft/s) to miles per hour (mph) and back, with the exact unit definitions.

- Page: https://www.acalculator.org/convert/fps-to-mph
- JSON spec: https://www.acalculator.org/convert/fps-to-mph.json
- Version: 57a4b92c2bd1

## Default answer

Example with the default inputs (Feet per second (ft/s) 1): 1 ft/s = 0.681818 mph.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| value | Feet per second (ft/s) | The amount in feet per second to convert. |
| result | Miles per hour (mph) | The same amount in miles per hour. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| value | Feet per second (ft/s) | The amount in feet per second to convert. |
| result | Miles per hour (mph) | The amount in miles per hour. |

## Method

mph = ft/s × 0.681818181818

## Assumptions

- 1 foot per second = 0.681818181818 miles per hour, 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; an answer of 1 billion or more shows at most 15 significant digits.

## Worked examples

1. value = 1 gives result = 0.681818. Source: Exact unit definitions in NIST SP 811 (2008), Appendix B.8.
2. value = 88 gives result = 60. Source: Exact unit definitions in NIST SP 811 (2008), Appendix B.8.
3. result = 60 gives value = 88. Source: Exact unit definitions in NIST SP 811 (2008), Appendix B.8.

## FAQ

### How many miles per hour are in a foot per second?

1 foot per second is 0.681818 miles per hour, from the exact unit definitions (NIST SP 811).

### How do I convert fps to mph?

Multiply by 0.681818: mph = ft/s × 0.681818181818. For example, 1 ft/s × 0.681818 = 0.681818 mph.

### How do I convert mph back to fps?

Multiply by 1.466667, or type the miles per hour into the second box and the converter works it out. 1 mile per hour is 1.466667 feet per second.

### Why multiply by 0.681818?

1 ft/s is 0.3048 m/s and 1 mph is 1,609.344 m ÷ 3,600 s = 0.44704 m/s (NIST SP 811). So 1 ft/s = 0.3048 ÷ 0.44704 = 15/22 mph exactly, 0.681818… mph.

### What is 88 ft/s in mph?

60 mph exactly: 88 × 15/22. 44 ft/s is 30 mph.

### Is fps frames per second here?

No. On this page fps means feet per second (ft/s), a speed. Frames per second count video frames and do not convert to mph.

## Sources

- NIST SP 811 (2008), Guide for the Use of the International System of Units, Appendix B.8: Factors for Units Listed Alphabetically (bold factors are exact), retrieved 2026-10-19. https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors/nist-guide-si-appendix-b8
- NIST, U.S. Survey Foot: Revised Unit Conversion Factors: 1 acre = 43,560 ft² = 4,046.856 422 4 m² and 1 mile = 5,280 ft = 1,609.344 m, exact with the international foot, retrieved 2026-10-19. https://www.nist.gov/pml/us-surveyfoot/revised-unit-conversion-factors