# Yeast Conversion Calculator

> Converts an amount of instant, active dry or fresh (cake) yeast into the equivalent amounts of the other two types by weight (instant 1 : active dry 1.25 : fresh 3) and expresses them in grams, teaspoons, 7 g packets and 17 g cakes.

- Calculator id: `yeast-conversion` · Category: Food & Cooking (`food`) · Tool name: `convert_yeast_types`
- Canonical page: https://tttkmbb.com/food/yeast-conversion · This document: https://tttkmbb.com/food/yeast-conversion.md · JSON definition: https://tttkmbb.com/food/yeast-conversion.json

## Purpose

Converts an amount of instant, active dry or fresh (cake) yeast into the equivalent amounts of the other two types by weight (instant 1 : active dry 1.25 : fresh 3) and expresses them in grams, teaspoons, 7 g packets and 17 g cakes.

**Use when:** A recipe calls for one type of yeast and you have another, or you need to convert between packets, teaspoons and grams of yeast.

**Do not use when:** You need the yeast amount for a dough from baker's percentages (use pizza-dough or bakers-percentage), or you are working with sourdough starter, brewing yeast or nutritional yeast.

## Input

| Parameter | Type | Unit | Required | Description |
| --- | --- | --- | --- | --- |
| `amount` | number |  | required | Quantity of yeast you have or the recipe calls for, in unit. (> 0, max 10000) |
| `unit` | enum: g \| tsp \| packet |  | optional, default "g" | Unit of amount; a packet means a 7 g (¼ oz) dry-yeast packet, or a 17 g (0.6 oz) cake when yeast_type is fresh_cake. |
| `yeast_type` | enum: instant \| active_dry \| fresh_cake |  | required | Type of the yeast given by amount. |

## Output

| Field | Type | Unit | Description |
| --- | --- | --- | --- |
| `instant_g` | number | g | Equivalent instant yeast. |
| `active_dry_g` | number | g | Equivalent active dry yeast (1.25 × instant). |
| `fresh_g` | number | g | Equivalent fresh (cake) yeast (3 × instant). |
| `instant_tsp` | number | tsp | instant_g / 3.1. |
| `active_dry_tsp` | number | tsp | active_dry_g / 3.1. |
| `instant_packets` | number | packets | instant_g / 7 g. |
| `active_dry_packets` | number | packets | active_dry_g / 7 g. |
| `fresh_cakes` | number | cakes | fresh_g / 17 g (US 0.6 oz cake). |
| `note` | string |  | Handling differences between the yeast types. |

## Formula

`grams = amount × (1 for g; 3.1 for tsp; 7 for a dry packet; 17 for a fresh cake); instant_g = grams / (1 instant, 1.25 active dry, 3 fresh); active_dry_g = 1.25 × instant_g; fresh_g = 3 × instant_g; tsp = g / 3.1; packets = g / 7; cakes = fresh_g / 17`

Weight ratios follow manufacturer guidance (Red Star, King Arthur Baking): fresh yeast has about one third of the leavening power of instant yeast per gram and active dry about 80 %. One level teaspoon of dry yeast is taken as 3.1 g (a 7 g packet is 2¼ teaspoons); a US fresh-yeast cake is 0.6 oz (17 g), European blocks are 42 g.

## Data Sources

- Red Star Yeast – Yeast conversion table (¼ oz packet = 2¼ tsp = 7 g; dry vs cake yeast) — https://redstaryeast.com/yeast-baking-lessons/yeast-conversion-table/ (reference, retrieved 2026-09-24)
- Wikipedia – Baker's yeast (instant, active dry and fresh yeast; substitution ratios) — https://en.wikipedia.org/wiki/Baker%27s_yeast (reference, retrieved 2026-09-24)
- King Arthur Baking – Ingredient weight chart — https://www.kingarthurbaking.com/learn/ingredient-weight-chart (reference, retrieved 2026-09-24)

Data freshness: `static`. Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output.

## API

- `GET https://tttkmbb.com/api/v1/calculate/yeast-conversion?amount=…&yeast_type=…`
- `POST https://tttkmbb.com/api/v1/calculate/yeast-conversion` with JSON body `{"inputs": {…}}`
- Response: unified envelope (`success`, `request`, `result.values`, `result.units`, `sources`, `freshness`, `timestamp`, `next_actions`, `links`); see https://tttkmbb.com/docs/response-format.md
- Schema: https://tttkmbb.com/api/v1/calculators/yeast-conversion · OpenAPI operationId `convert_yeast_types` in https://tttkmbb.com/openapi.json
- Authentication: none. Rate limit: fair use, see https://tttkmbb.com/docs/rate-limits.md.

## MCP

- Server: `https://tttkmbb.com/mcp` (Streamable HTTP, JSON-RPC 2.0, no auth)
- Tool:  `run_calculator` with `{"calculator_id": "yeast-conversion", "inputs": {…}}`

## Example

- 7 g instant yeast: inputs `{"amount":7,"unit":"g","yeast_type":"instant"}` → `{"instant_g":7,"active_dry_g":8.75,"fresh_g":21,"instant_tsp":2.26,"active_dry_tsp":2.82,"instant_packets":1,"fresh_cakes":1.24}`
- 1 packet active dry yeast: inputs `{"amount":1,"unit":"packet","yeast_type":"active_dry"}` → `{"active_dry_g":7,"instant_g":5.6,"fresh_g":16.8,"instant_tsp":1.81,"active_dry_packets":1,"fresh_cakes":0.99}`

```
GET https://tttkmbb.com/api/v1/calculate/yeast-conversion?amount=7&unit=g&yeast_type=instant
```

## Limitations

You need the yeast amount for a dough from baker's percentages (use pizza-dough or bakers-percentage), or you are working with sourdough starter, brewing yeast or nutritional yeast. Weight ratios follow manufacturer guidance (Red Star, King Arthur Baking): fresh yeast has about one third of the leavening power of instant yeast per gram and active dry about 80 %. One level teaspoon of dry yeast is taken as 3.1 g (a 7 g packet is 2¼ teaspoons); a US fresh-yeast cake is 0.6 oz (17 g), European blocks are 42 g. All values are computed from the formula above; no measurement or live data is involved.

## FAQ

**Can I swap instant and active dry yeast 1:1?**

In practice yes for most bread recipes; the 25 % difference is within the normal variation of rise times. Use the exact conversion for large batches or when timing matters.

**Why is a 7 g packet 2¼ teaspoons but the calculator shows 2.26?**

Because 3.1 g per teaspoon is a rounded average (7 g / 2.25 tsp = 3.11 g); the difference is far below what a measuring spoon can resolve.

**How do I use fresh yeast?**

Crumble it into the recipe's lukewarm liquid (or directly into the dough) and use within its short shelf life (about 2 weeks refrigerated); it should smell yeasty, not sour.

## Related

- [Pizza Dough Calculator](https://tttkmbb.com/food/pizza-dough.md) — Yeast amount for pizza dough by baker's percentage.
- [Baker's Percentage Calculator](https://tttkmbb.com/food/bakers-percentage.md) — Scale yeast with the rest of a bread formula.
- [Baking Substitution Calculator](https://tttkmbb.com/food/baking-substitutions.md) — Substitutes for other baking ingredients.