# US cups to US fluid ounces (cup to fl oz)

> Convert US cups to US fluid ounces: 1 cup = 8 fl oz. Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.

- Page id: `cups-to-fl-oz` · Quantity: Volume (`volume`, base unit L) · Tool: `convert_units`
- Canonical page: https://tttkmbb.com/conversion/cups-to-fl-oz · This document: https://tttkmbb.com/conversion/cups-to-fl-oz.md · JSON: https://tttkmbb.com/conversion/cups-to-fl-oz.json (add `?value=` for a result)

## Formula

- `1 cup = 8 fl oz`
- `US fluid ounces = US cups × 8`
- Reverse: `US cups = US fluid ounces × 0.125`

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 cup = 40 fl oz
- 12.5 cup = 100 fl oz
- 100 cup = 800 fl oz

## Conversion table

| US cups (cup) | US fluid ounces (fl oz) |
| --- | --- |
| 1 | 8 |
| 2 | 16 |
| 3 | 24 |
| 4 | 32 |
| 5 | 40 |
| 6 | 48 |
| 7 | 56 |
| 8 | 64 |
| 9 | 72 |
| 10 | 80 |
| 15 | 120 |
| 20 | 160 |
| 25 | 200 |
| 30 | 240 |
| 40 | 320 |
| 50 | 400 |
| 75 | 600 |
| 100 | 800 |
| 200 | 1600 |
| 250 | 2000 |
| 500 | 4000 |
| 1000 | 8000 |

## API

- `GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=cup_us&to_unit=fl_oz_us` → 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":"cup_us","to_unit":"fl_oz_us"}`
- All volume units: https://tttkmbb.com/api/v1/units?quantity=volume · full converter: [Volume Converter](https://tttkmbb.com/conversion/volume.md)
- Authentication: none. Freshness: `static` (fixed conversion factors).

## FAQ

**How many US fluid ounces are in one cup?**

1 cup = 8 fl oz. 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 US cups to US fluid ounces?**

Multiply the value in US cups by 8: US fluid ounces = US cups × 8. For example, 5 cup = 40 fl oz.

**How do I convert US fluid ounces back to US cups?**

Multiply by the inverse factor 0.125 (US cups = US fluid ounces × 0.125), or use the US fluid ounces-to-US cups page.

## Related conversions

- [US fluid ounces to US cups](https://tttkmbb.com/conversion/fl-oz-to-cups.md) (reverse)
- [Liters to US gallons](https://tttkmbb.com/conversion/liters-to-gallons.md)
- [US gallons to Liters](https://tttkmbb.com/conversion/gallons-to-liters.md)
- [Milliliters to US fluid ounces](https://tttkmbb.com/conversion/ml-to-fl-oz.md)
- [US fluid ounces to Milliliters](https://tttkmbb.com/conversion/fl-oz-to-ml.md)
- [Liters to Milliliters](https://tttkmbb.com/conversion/liters-to-ml.md)
- [Milliliters to Liters](https://tttkmbb.com/conversion/ml-to-liters.md)
- [US cups to Milliliters](https://tttkmbb.com/conversion/cups-to-ml.md)
- [Milliliters to US cups](https://tttkmbb.com/conversion/ml-to-cups.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)