# How to convert oz to grams?

Converts ounces (oz) to grams (g) and back, with the exact unit definitions.

- Page: https://www.acalculator.org/convert/oz-to-grams
- JSON spec: https://www.acalculator.org/convert/oz-to-grams.json
- Version: be0c6d5bbf88

## Default answer

Example with the default inputs (Ounces (oz) 1): 1 oz = 28.349523 g.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| value | Ounces (oz) | The amount in ounces to convert. |
| result | Grams (g) | The same amount in grams. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| value | Ounces (oz) | The amount in ounces to convert. |
| result | Grams (g) | The amount in grams. |

## Method

g = oz × 28.349523125

## Assumptions

- 1 ounce = 28.349523125 grams, from the exact definitions in NIST SP 811.
- Ounces here are avoirdupois ounces, a weight: 1 oz = 1/16 lb = 28.349523125 g. A US fluid ounce is a volume.
- 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 = 28.349523. Source: Exact unit definitions in NIST SP 811 (2008), Appendix B.8.
2. value = 16 gives result = 453.59237. Source: Exact unit definitions in NIST SP 811 (2008), Appendix B.8.
3. result = 453.59237 gives value = 16. Source: Exact unit definitions in NIST SP 811 (2008), Appendix B.8.

## FAQ

### How many grams are in an ounce?

1 ounce is 28.349523 grams, from the exact unit definitions (NIST SP 811).

### How do I convert oz to grams?

Multiply by 28.349523: g = oz × 28.349523125. For example, 1 oz × 28.349523 = 28.349523 g.

### How do I convert grams back to oz?

Multiply by 0.035274, or type the grams into the second box and the converter works it out. 1 gram is 0.035274 ounces.

### Is an ounce here a weight or a volume?

A weight: the avoirdupois ounce, 1/16 of a pound (28.349523125 g exactly). A US fluid ounce (29.57 mL) measures volume, as on cups-to-ounces pages.

### What is 16 oz in grams?

453.59237 g, exactly 1 pound: 16 × 28.349523125.

### What is 4 oz in grams?

113.398093 g: 4 × 28.349523125. A quick estimate of 28 g an ounce is 1.2% low.

## 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 2026-10-18. https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors/nist-guide-si-appendix-b8
- NIST SP 811 (2008), footnotes to Appendix B: 1 lb = 0.45359237 kg exactly (footnote 22); 1 lbf = 4.4482216152605 N exactly with standard gravity, 9.80665 m/s² (footnote 23), retrieved 2026-10-18. https://www.nist.gov/pml/special-publication-811/nist-guide-si-footnotes