---
title: "OD600 to cells/mL"
method: POST
path: "/od600_cells"
tags: ["Analysis"]
---

# OD600 to cells/mL

`POST /od600_cells`

## Request

- Base URL: `https://seqbench.com/api/v1`
- URL: `https://seqbench.com/api/v1/od600_cells`
- Auth: none required

Convert an OD600 reading to a cell density and a total cell count, correcting for the optical path and any dilution, and flagging the two things that silently make the number wrong: a reading above the linear range (a dense culture reads LOW), and a plate-reader path length assumed to be a cuvette's 1 cm. Also plans a back-dilution to a target OD. The cells-per-OD factor is a convention, not a constant — it varies with strain, growth phase and instrument, so pass factorPerOd when you have calibrated against plate counts.

## Request body

- object
  - `od600` number, required: The reading off the spectrophotometer.
  - `organism` 'ecoli' | 'scerevisiae' | 'ppastoris': Supplies the cells-per-OD factor. Ignored when factorPerOd is given.
  - `factorPerOd` number: Your own calibration: cells/mL at OD600 = 1.0 in a 1 cm path. Overrides organism.
  - `pathLengthCm` number: Optical path of the reading. A cuvette is 1 cm; 200 µL in a 96-well flat plate is about 0.58 cm.
  - `dilutionFactor` number: Dilution done before reading (2 means the sample was diluted 1:2).
  - `volumeMl` number: Culture volume, for a total cell count. 0 = not given.
  - `targetOd` number: Optional: plan a back-dilution to this OD. 0 = skip.
  - `targetVolumeMl` number: Final volume for the back-dilution plan.

## Response `200`

Tool ran successfully.

- SuccessResponse: Standard success envelope returned by every single-tool call.
  - `ok` unknown, required
  - `tool` string, required: The tool slug that ran.
  - `result` object, required: Tool-specific output object. Its shape depends on the tool — call `GET /{tool}` or see the docs for each tool's fields.
  - `gate` GateResult
    - `pass` boolean, required: True if and only if every hard check passed.
    - `checks` GateCheck[], required
      - `id` string, required
      - `label` string, required
      - `severity` 'hard' | 'soft', required
      - `pass` boolean, required
      - `message` string, required
      - `value` number
      - `threshold` string
    - `notChecked` string[], required: Honest list of what this gate does NOT verify.
  - `provenance` Provenance, required
    - `apiVersion` string, required
    - `tool` union, required: Tool slug, or an array of slugs (one per step) for a workflow.
      - string
      - string[]
    - `generatedAt` string, date-time, required: ISO 8601 timestamp of when the result was generated.

## Other responses

- `400`: Invalid argument or the tool could not run.
- `404`: Unknown tool.
- `429`: Rate limited (metered tools only). Body carries code `rate_limited` and retryable `true`; honor the Retry-After header.
- `503`: A metered tool is momentarily at capacity. The identical request should succeed after Retry-After; body carries code `upstream_unavailable`.

---

[API](https://skmtc.dev/seqbench/apis/seqbench-api.md) · [All operations](https://skmtc.dev/seqbench/apis/seqbench-api/llms.txt) · [OpenAPI document](https://skmtc.dev/seqbench/apis/seqbench-api/revisions/132575216865?raw)