> This page is for Developer Documentation.

> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs.benchling.com/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.benchling.com/_mcp/server.

# Create UnitType

POST https://{tenant_name}.benchling.com/api/v3/unit-type
Content-Type: application/json

Create UnitType.

Reference: https://docs.benchling.com/docs/api/benchling-api/unit-type/create

## Authentication

- `Authorization` header (bearer token, required) — Bearer authentication of the form `Bearer <token>`, where token is your auth token.

## Request

### Body (application/json)

This endpoint expects a CreateUnitTypeInput.

- `baseUnit` (CreateBaseUnitInput, required) — The reference unit for this type.
- `name` (string, required) — The name of this unit type, e.g. "Volume".
- `overrideIsConcentration` (boolean, required) — When true, forces this UnitType to be treated as a concentration type regardless of its terms. When false, the classification is determined by the UnitType's terms. Mutually exclusive with overrideIsContainerQuantity.
- `overrideIsContainerQuantity` (boolean, required) — When true, forces this UnitType to be treated as a container quantity type regardless of its terms. When false, the classification is determined by the UnitType's terms. Mutually exclusive with overrideIsConcentration.
- `formula` (list of CreateFormulaUnitTermInput, optional) — Formula defining this type in terms of other units.

## Response

### 201

Created

- `__typename` (string, optional)
- `archiveReason` (string, optional, nullable)
- `archived` (boolean, optional)
- `baseUnit` (UnitRef, optional, nullable) — The reference unit. All other units' conversionFactors are relative to this unit. Null for unit types with no units yet.
- `createdAt` (string, optional, nullable)
- `formula` (list of FormulaUnitTerm, optional, nullable) — Defines this unit type in terms of other units for derived types, e.g. Liter = decimeter cubed.
- `id` (string, optional)
- `modifiedAt` (string, optional, nullable)
- `name` (string, optional) — The user-facing name, e.g. "Volume" or "Molar Concentration".
- `overrideIsConcentration` (boolean, optional, nullable) — When true, forces this UnitType to be treated as a concentration type regardless of its terms. When false, the classification is determined by the UnitType's terms. Mutually exclusive with `overrideIsContainerQuantity`.
- `overrideIsContainerQuantity` (boolean, optional, nullable) — When true, forces this UnitType to be treated as a container quantity type regardless of its terms. When false, the classification is determined by the UnitType's terms. Mutually exclusive with `overrideIsConcentration`.
- `terms` (list of UnitTypeTerm, optional) — The dimensional composition of this unit type as a list of SI base dimensions with exponents.
- `units` (string, optional, nullable) — All units belonging to this unit type.

## Errors

### 400 Unit Type Create Request Bad Request Error

Bad Request

- `detail` (GeneralErrorDetail, required, nullable)
- `instance` (string, required)
- `status` (integer, required)
- `title` (string, required, nullable)
- `type` (string, required)
- `invalidId` (string, optional)

### 403 Unit Type Create Request Forbidden Error

Forbidden

- `detail` (GeneralErrorDetail, required, nullable)
- `instance` (string, required)
- `status` (integer, required)
- `title` (string, required, nullable)
- `type` (string, required)
- `invalidId` (string, optional)

### 404 Unit Type Create Request Not Found Error

Not Found

- `detail` (GeneralErrorDetail, required, nullable)
- `instance` (string, required)
- `status` (integer, required)
- `title` (string, required, nullable)
- `type` (string, required)
- `invalidId` (string, optional)

### 409 Unit Type Create Request Conflict Error

Conflict

- `detail` (GeneralErrorDetail, required, nullable)
- `instance` (string, required)
- `status` (integer, required)
- `title` (string, required, nullable)
- `type` (string, required)
- `invalidId` (string, optional)

### 429 Unit Type Create Request Too Many Requests Error

Too Many Requests

- `detail` (TooManyRequestsErrorBodyDetail, required, nullable)
- `instance` (string, required)
- `status` (integer, required)
- `title` (string, required, nullable)
- `type` (string, required)
- `invalidId` (string, optional)
- `violated-policies` (list of enum, optional) — The budget policies that rejected the request, in canonical order: `user`, `integration`, then `tenant`.
  - Allowed values: `user`, `integration`, `tenant`

### 500 Unit Type Create Request Internal Server Error

Internal Server Error

- `detail` (InternalServerErrorBodyDetail, required, nullable)
- `instance` (string, required)
- `status` (integer, required)
- `title` (string, required, nullable)
- `type` (string, required)
- `errorId` (string, optional)

## Types

### CreateBaseUnitInput

- `aliases` (list of string, required) — Alternative abbreviations for this unit, i.e. alternate symbols.
- `name` (string, required) — The long-form name, e.g. "milliliter".
- `symbol` (string, required) — The short-form label, e.g. "mL".

### CreateFormulaUnitTermInput

- `exponent` (integer, required) — The exponent applied to the unit.
- `value` (string, required) — The API ID of the unit in this formula term.

### UnitRef

- `__typename` (string, optional)
- `id` (string, optional)

### FormulaUnitTerm

A term in the original formula of a `UnitType` that references an actual `Unit` rather than a base dimension. This is used to define relationships between units across different UnitTypes, such as defining that Liter = decimeter³. Unlike `UnitTypeTerm` which uses abstract SI dimensions, FormulaUnitTerm references concrete Unit definitions and is the crucial piece for establishing mathematical relationships when composing derived unit types.

- `__typename` (string, optional)
- `exponent` (integer, optional)
- `value` (UnitRef, optional)

### UnitTypeTerm

A term in the dimensional formula of a `UnitType`, pairing one of the seven SI base dimensions (see `BaseUnitType`) with an integer exponent. Multiple terms together describe the dimensional composition of a UnitType. For example, a Volume UnitType would have a single term with value=LENGTH and exponent=3, while Acceleration would have [LENGTH^1, TIME^-2]. Terms are descriptive metadata and do not uniquely identify a UnitType—multiple UnitTypes can share the same dimensional terms.

- `__typename` (string, optional)
- `exponent` (integer, optional)
- `value` (enum, optional)
  - Allowed values: `TIME`, `LENGTH`, `MASS`, `CURRENT`, `TEMPERATURE`, `AMOUNT`, `LUMINOUS_INTENSITY`

### GeneralErrorDetail

### TooManyRequestsErrorBodyDetail

### InternalServerErrorBodyDetail

## Examples

**Request**

```json
{
  "baseUnit": {
    "aliases": [
      "aliases"
    ],
    "name": "name",
    "symbol": "symbol"
  },
  "name": "name",
  "overrideIsConcentration": true,
  "overrideIsContainerQuantity": true
}
```

**Response**

```json
{
  "__typename": "__typename",
  "archiveReason": "archiveReason",
  "archived": true,
  "baseUnit": {
    "__typename": "__typename",
    "id": "id"
  },
  "createdAt": "createdAt",
  "formula": [
    {
      "__typename": "__typename",
      "exponent": 1
    }
  ],
  "id": "id",
  "modifiedAt": "modifiedAt",
  "name": "name",
  "overrideIsConcentration": true,
  "overrideIsContainerQuantity": true,
  "terms": [
    {
      "__typename": "__typename",
      "exponent": 1,
      "value": "TIME"
    }
  ],
  "units": "units"
}
```

**SDK Code**

```python
import requests

url = "https://{tenant_name}.benchling.com/api/v3/unit-type"

payload = {
    "baseUnit": {
        "aliases": ["aliases"],
        "name": "name",
        "symbol": "symbol"
    },
    "name": "name",
    "overrideIsConcentration": True,
    "overrideIsContainerQuantity": True
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.json())
```

```javascript
const url = 'https://{tenant_name}.benchling.com/api/v3/unit-type';
const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: '{"baseUnit":{"aliases":["aliases"],"name":"name","symbol":"symbol"},"name":"name","overrideIsConcentration":true,"overrideIsContainerQuantity":true}'
};

try {
  const response = await fetch(url, options);
  const data = await response.json();
  console.log(data);
} catch (error) {
  console.error(error);
}
```