# Henderson-Hasselbalch Calculator API

> For the complete documentation index, see [llms.txt](/llms.txt).

Buffer pH from pKa and the conjugate base/acid ratio, or solve for the ratio or the pKa, via the Henderson-Hasselbalch equation.

Use this endpoint to add the tool to your app, site, workflow, or agent without rebuilding formulas, validation, examples, and docs.

- Slug: `henderson-hasselbalch-calculator`
- Category: `science`
- Version: `2026-04-22`
- Credits per successful call: 1
- Starts on: free
- Max payload: 65536 bytes
- Privacy mode: `hash_only`
- Available on: free, starter, pro, business, scale
- Browser tool: https://miniwebtool.com/henderson-hasselbalch-calculator/

## Endpoint

`POST https://api.miniwebtool.com/v1/tools/henderson-hasselbalch-calculator/run`

## Request body

| Field | Type | Required | Description |
| --- | --- | --- | --- |
| `mode` | `str` | no | ph | ratio | pka Choices: ph, ratio, pka |
| `pka` | `float | None` | no | acid dissociation constant exponent |
| `base_conc` | `float | None` | no | conjugate base concentration, mol/L |
| `acid_conc` | `float | None` | no | weak acid concentration, mol/L |
| `target_ph` | `float | None` | no | target pH, required for mode=ratio |
| `ph` | `float | None` | no | measured pH, required for mode=pka |

## Example request

```json
{
  "mode": "ph",
  "pka": 4.76,
  "base_conc": 0.1,
  "acid_conc": 0.1
}
```

## cURL

```bash
curl -X POST https://api.miniwebtool.com/v1/tools/henderson-hasselbalch-calculator/run \
  -H 'Authorization: Bearer mwt_live_YOUR_KEY' \
  -H 'Content-Type: application/json' \
  -d '{"mode":"ph","pka":4.76,"base_conc":0.1,"acid_conc":0.1}'
```

## Response envelope

```json
{
  "request_id": "01K...",
  "tool": "henderson-hasselbalch-calculator",
  "tool_version": "2026-04-22",
  "credits_used": 1,
  "result": {}
}
```

## Errors

Errors are RFC 7807 `application/problem+json`. Branch on `code`, not `title`.

## MCP

Agents can discover and call this tool through `https://api.miniwebtool.com/mcp` or `https://api.miniwebtool.com/v1/mcp` using MCP `tools/list` and `tools/call`.

## Frequently asked

### What does the Henderson-Hasselbalch Calculator API do?

Buffer pH from pKa and the conjugate base/acid ratio, or solve for the ratio or the pKa, via the Henderson-Hasselbalch equation. Use it to add this utility without rebuilding formulas, validation, examples, and documentation.

### How much does one call cost?

1 credit per successful call. Failed calls do not bill.

### What parameters are required?

Required fields: (none). Full schema at `https://api.miniwebtool.com/v1/openapi.json`.

### Is this deterministic?

Yes. Same input, same output. Tool version: 2026-04-22.