# Duration convert

`duration-convert` · version 1.0.0 · Dates & times (UTC, ISO 8601) · free, no key needed

Convert a canonical integer duration between nanosecond-based SI units as an exact rational.

**Use when you need to: duration convert · convert duration units · convert seconds minutes hours days.**

## Supported

- duration convert
- convert duration units
- convert seconds minutes hours days

## Not supported

- months
- years
- weeks
- leap seconds
- ISO-8601 duration strings
- floats
- calendar dates

## Behavior

- value is a canonical integer string amount in the from unit; -0 is accepted and canonicalized to 0.
- Units are ns, us, ms, s, min, h, and day from DURATION_NS; day is exactly 86400 seconds.
- Conversion is the exact rational value * from_ns / to_ns, reduced with sign only on the numerator.
- Negative durations are allowed; leap seconds, months, years, and ISO-8601 duration strings are rejected.
- Input integers and the reduced numerator and denominator may have at most 1000 digits excluding sign.

## Input

- `value` (string, required): max length 1001; pattern `^-?(0|[1-9][0-9]*)$`
- `from` (one of "ns", "us", "ms", "s", "min", "h", "day", required)
- `to` (one of "ns", "us", "ms", "s", "min", "h", "day", required)

## Output

- `numerator` (string, required): pattern `^(0|-?[1-9][0-9]*)$`
- `denominator` (string, required): pattern `^[1-9][0-9]*$`

## Limits

- max digits: 1000
- units: ["ns","us","ms","s","min","h","day"]

## Example

Request input:

```json
{
  "value": "90",
  "from": "s",
  "to": "min"
}
```

Response:

```json
{
  "result": {
    "numerator": "3",
    "denominator": "2"
  }
}
```

## How to call it

### MCP

Connect `https://computefirst.net/mcp` ([setup](/docs#connect)), then call `execute` with:

```json
{
  "id": "duration-convert",
  "version": "1.0.0",
  "input": {
    "value": "90",
    "from": "s",
    "to": "min"
  }
}
```

### HTTP (no key)

```sh
curl -X POST https://computefirst.net/v1/tools/duration-convert/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"value":"90","from":"s","to":"min"}'
```

The machine-readable contract is at [/v1/tools/duration-convert/versions/1.0.0](/v1/tools/duration-convert/versions/1.0.0).

### CLI

```sh
node cli.mjs run duration-convert 1.0.0 --input input.json --base-url https://computefirst.net
```

Get the client at [/clients/cli/](/clients/cli/).

## Related tools

- [Duration add](/tools/duration-add): Sum mixed SI duration terms in nanoseconds and return the exact rational in a target unit.
- [Duration compare](/tools/duration-compare): Compare two SI duration amounts after converting both to nanoseconds.
- [ISO date add](/tools/iso-date-add): Add a signed whole-day delta to a strict YYYY-MM-DD calendar date.
- [ISO date age](/tools/iso-date-age): Compute the calendar-aware elapsed years, months, and days between a birth date and an as-of date.
- [ISO date business day add](/tools/iso-date-business-day-add): Add a signed count of business days to a date, skipping caller-supplied weekend weekdays and holidays.
- [ISO date business days count](/tools/iso-date-business-days-count): Count the business days in an inclusive date range, skipping caller-supplied weekend weekdays and holidays.