# Scientific Notation API
> Scientific number representation as an API. The scientific endpoint expresses a number in both scientific notation (one digit before the decimal point × a power of ten) and engineering notation (the exponent a multiple of three, lining up with SI prefixes), and reports the mantissa and exponent. The sigfigs endpoint rounds a number to a chosen number of significant figures, and counts the significant figures in a value — respecting the rules for leading zeros, trailing zeros and the decimal point, and flagging the ambiguous cases such as "1200". The si-prefix endpoint formats a number with the right metric prefix (1500 → 1.5 k, 2.3×10⁹ → 2.3 G, 0.0023 → 2.3 m) with an optional unit, and parses a prefixed value back to a plain number (2.2 MΩ → 2,200,000). Everything is computed locally and deterministically, so it is instant and private. Ideal for science and engineering tools, lab and measurement software, electronics and signal work, and education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 4 endpoints. This is scientific number representation; for locale number formatting use a number-format API and for number-to-words or Roman numerals use a number API.

## Authentication
All requests require your oanor API key in the `x-oanor-key` header. Get one at https://www.oanor.com/developer/keys.

```bash
curl -H "x-oanor-key: oanor_live_…" "https://api.oanor.com/sigfig-api/..."
```

## Pricing
- **Free** (Free) — 8,635 calls/Mo, 2 req/s
- **Starter** ($10/Mo) — 18,150 calls/Mo, 8 req/s
- **Pro** ($30/Mo) — 232,500 calls/Mo, 20 req/s
- **Mega** ($68/Mo) — 1,205,000 calls/Mo, 50 req/s

## Endpoints

### Numbers

#### `GET /v1/scientific` — Scientific & engineering notation

**Parameters:**
- `value` (query, required, string) — A number Example: `1500`
- `sigfigs` (query, optional, string) — Mantissa sig figs (default 6)

**Example:**
```bash
curl -H "x-oanor-key: $KEY" \
  "https://api.oanor.com/sigfig-api/v1/scientific?value=1500"
```

**Response:**
```json
{
    "data": {
        "value": 1500,
        "exponent": 3,
        "mantissa": 1.5,
        "scientific": "1.5e+3",
        "engineering": "1.5e+3",
        "scientific_pretty": "1.5 × 10^3",
        "engineering_pretty": "1.5 × 10^3",
        "engineering_exponent": 3,
        "engineering_mantissa": 1.5
    },
    "meta": {
        "timestamp": "2026-06-03T17:42:03.238Z",
        "request_id": "74cbd299-d352-40ec-bf45-55417200cfee"
    },
    "status": "ok",
    "message": "Scientific notation",
    "success": true
}
```

#### `GET /v1/si-prefix` — SI metric prefix

**Parameters:**
- `value` (query, optional, string) — A number Example: `2300000000`
- `unit` (query, optional, string) — Optional unit Example: `Hz`
- `parse` (query, optional, string) — Or a prefixed string Example: `2.2 MΩ`

**Example:**
```bash
curl -H "x-oanor-key: $KEY" \
  "https://api.oanor.com/sigfig-api/v1/si-prefix?value=2300000000&unit=Hz&parse=2.2+M%CE%A9"
```

**Response:**
```json
{
    "data": {
        "input": "2.2 MΩ",
        "value": 2200000,
        "prefix": "M"
    },
    "meta": {
        "timestamp": "2026-06-03T17:42:03.344Z",
        "request_id": "12216ad6-62ca-4238-b132-8aef030314f8"
    },
    "status": "ok",
    "message": "SI prefix",
    "success": true
}
```

#### `GET /v1/sigfigs` — Round / count significant figures

**Parameters:**
- `value` (query, required, string) — A number Example: `3.14159`
- `round_to` (query, optional, string) — Round to N sig figs Example: `3`

**Example:**
```bash
curl -H "x-oanor-key: $KEY" \
  "https://api.oanor.com/sigfig-api/v1/sigfigs?value=3.14159&round_to=3"
```

**Response:**
```json
{
    "data": {
        "value": "3.14159",
        "rounded": 3.14,
        "round_to": 3,
        "rounded_string": "3.14",
        "significant_figures": {
            "note": "trailing zeros after a decimal point are significant",
            "count": 6
        }
    },
    "meta": {
        "timestamp": "2026-06-03T17:42:03.452Z",
        "request_id": "4da87a57-16c9-4ed1-83f1-ffa7c589f00d"
    },
    "status": "ok",
    "message": "Significant figures",
    "success": true
}
```

### Meta

#### `GET /v1/meta` — Spec

**Example:**
```bash
curl -H "x-oanor-key: $KEY" \
  "https://api.oanor.com/sigfig-api/v1/meta"
```

**Response:**
```json
{
    "data": {
        "name": "Scientific Notation API",
        "notes": "Engineering notation uses exponents that are multiples of 3. SI prefixes from yocto (10⁻²⁴) to yotta (10²⁴). µ and u both mean micro. Nothing is stored.",
        "version": "v1",
        "endpoints": [
            {
                "path": "/v1/scientific",
                "params": {
                    "value": "a number",
                    "sigfigs": "mantissa significant figures (default 6)"
                },
                "returns": "scientific and engineering notation"
            },
            {
                "path": "/v1/sigfigs",
                "params": {
                    "value": "a number",
                    "round_to": "round to N significant figures"
                },
                "returns": "the rounded value and/or the significant-figure count"
            },
            {
                "path": "/v1/si-prefix",
                "params": {
                    "unit": "optional unit",
                    "parse": "or a prefixed string to parse",
                    "value": "a number"
                },
                "returns": "the SI-prefixed form (or the parsed value)"
            },
            {
                "path": "/v1/meta",
                "params": [],
                "returns": "this document"
            }
        ],
        "description": "Scientific number representation as an API. The scientific endpoint expresses a number in both scient
…(truncated, see openapi.json for full schema)
```


---
Marketplace page: https://www.oanor.com/api/sigfig-api
OpenAPI spec: https://www.oanor.com/api/sigfig-api/openapi.json