Documentation sections

Aperture Diagonal & Drill Size Calculator

POSThttps://rftools.io/api/py/v1/calculate

Slug aperture-diagonal. Get the corner-to-corner diagonal of a rectangular aperture plus the stocked tool that covers it — the drill that clears the diagonal, or the cutter that fits the short side and the corner radius it leaves.

Inputs

Send every one of these in inputs, in the units shown. Most are required: a call without one is refused (400) and costs nothing; one the calculator can do without takes the default shown. An input outside its range is still computed and flagged in the provenance.

Inputs of aperture-diagonal
Name	Unit	Range	Default	Description
apertureLengthnumber	mm	0.05 … 500	2	Aperture Length
apertureWidthnumber	mm	0.05 … 500	1	Aperture Width
routerBitnumber	mm	0 … 10	0	The routing cutter your fabricator will use. Leave at 0 to take the largest stocked tool at or below the short side; the corner radius and the oval warning follow the cutter in use.

Outputs

Returned in values, by key. A value that is unbounded or undefined is null.

Outputs of aperture-diagonal
Field	Unit	Description
diagonalheadline	mm	Corner-to-Corner Diagonal
coveringDrillSize	mm	Next stocked tool at or above the diagonal — never the one below. Not reported when the diagonal exceeds the largest stocked drill.
drillOversize	mm	How much larger the stocked tool is than the exact requirement
shortSide	mm	Short Side
routerBitSize	mm	For routing the opening rather than drilling it: the fabricator's cutter when entered, otherwise the largest stocked tool that fits the short side
cornerRadius	mm	Half the cutter diameter — a routed rectangle never has sharp corners

Calling it

Calculate: one call, the request and response in full, and its errors.
Batch: this calculator with others, or a sweep, in one request.
Solve for a target: the value of one input that brings an output to a target.

curl -X POST https://rftools.io/api/py/v1/calculate \
  -H "X-API-Key: $RFTOOLS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "slug": "aperture-diagonal",
    "inputs": {
      "apertureLength": 2,
      "apertureWidth": 1,
      "routerBit": 0
    }
  }'

import rftools

client = rftools.Client()  # reads RFTOOLS_API_KEY, or the key `rftools login` saved

result = client.calculate("aperture-diagonal", {"apertureLength": 2, "apertureWidth": 1, "routerBit": 0})
print(result.values)
print(result.warnings, result.provenance.formula_ref)

const response = await fetch("https://rftools.io/api/py/v1/calculate", {
  method: "POST",
  headers: {
    "X-API-Key": process.env.RFTOOLS_API_KEY,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "slug": "aperture-diagonal",
    "inputs": {
      "apertureLength": 2,
      "apertureWidth": 1,
      "routerBit": 0
    }
  }),
});
console.log(response.status, await response.json());

package main

import (
	"bytes"
	"fmt"
	"io"
	"net/http"
	"os"
)

func main() {
	body := []byte(`{
	  "slug": "aperture-diagonal",
	  "inputs": {
	    "apertureLength": 2,
	    "apertureWidth": 1,
	    "routerBit": 0
	  }
	}`)
	req, err := http.NewRequest("POST", "https://rftools.io/api/py/v1/calculate", bytes.NewReader(body))
	if err != nil {
		panic(err)
	}
	req.Header.Set("X-API-Key", os.Getenv("RFTOOLS_API_KEY"))
	req.Header.Set("Content-Type", "application/json")
	res, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer res.Body.Close()
	out, _ := io.ReadAll(res.Body)
	fmt.Println(res.Status, string(out))
}

application/json

{
  "slug": "aperture-diagonal",
  "values": {
    "diagonal": 2.23606797749979,
    "shortSide": 1,
    "coveringDrillSize": 2.25,
    "drillOversize": 0.013932022500210195,
    "routerBitSize": 1,
    "cornerRadius": 0.5
  },
  "warnings": [
    "The corner radius the cutter leaves (0.500 mm) is a large fraction of the short side — the routed opening will read as an oval rather than a rectangle"
  ],
  "errors": [],
  "provenance": {
    "method": "calculator:aperture-diagonal",
    "version": "api@3f2c1a9b04de",
    "formulaRef": "Geometry; tooling grid is stocked metric PCB tooling in 0.05 mm steps. 1 in = 25.4 mm exactly.",
    "assumptions": [],
    "validRange": {
      "status": "inside",
      "bounds": {
        "apertureLength": {
          "min": 0.05,
          "max": 500,
          "unit": "mm"
        },
        "apertureWidth": {
          "min": 0.05,
          "max": 500,
          "unit": "mm"
        },
        "routerBit": {
          "min": 0,
          "max": 10,
          "unit": "mm"
        }
      },
      "outside": [],
      "model": null
    },
    "computedAt": "2026-09-24T14:05:11.003Z",
    "inputs": {
      "apertureLength": 2,
      "apertureWidth": 1,
      "routerBit": 0
    },
    "seed": null,
    "elapsedSeconds": 0.003
  }
}

{
  "detail": [
    {
      "type": "float_parsing",
      "loc": [
        "body",
        "inputs",
        "apertureLength"
      ],
      "msg": "Input should be a valid number, unable to parse string as a number",
      "input": "abc"
    }
  ]
}

An input sent as text. Nothing was counted.

{
  "detail": "More than 120 requests in 60 seconds from this address.",
  "errorKind": "rate_limited",
  "limit": 120,
  "windowSeconds": 60,
  "upgradeUrl": "https://rftools.io/pricing/"
}

Too many requests in a minute, with Retry-After.

Same inputs on the calculator pageAperture Diagonal & Drill Size Calculator, at these values