It’s a length converter, and for some reason, it’s like the if conditional. Here is the code :

let output_result = document.getElementById('output');
let input_value;
let inputtype;
let input_unit_type;
let output_unit_type;
var outputtype;
function convert() {
    input_value = parseFloat(document.getElementById('number_input').value);
    input_unit_type = parseInt(document.querySelector('input[name="unitconverting"]:checked').value);
    output_unit_type = parseInt(document.querySelector('input[name="unitconverted"]:checked').value);
//Convert Imperial Units to Inches
    switch (input_unit_type) {
        case 1: {
            output_value = input_value * 12;
            inputtype="imperial";
            break;
        };
        case 2: {
            output_value = input_value;
            inputtype="imperial";
            break;
        };
        case 3: {
            output_value = input_value * 36;
            inputtype="imperial";
            break;
        };
        case 4: {
            output_value = input_value * 63360;
            inputtype="imperial";
            break;
        };
//Convert Metric Units to centimeters
// 1 inch = 2.54 cm.
        //M to CM
        case 5: {
            output_value = (input_value * 100);
            inputtype="metric";
            break;
        };
        //CM to CM
        case 6: {
            output_value = input_value;
            inputtype="metric";
            break;
        };
        //MM to CM
        case 7: {
            output_value = (input_value / 10);
            inputtype="metric";
            break;
        };
        //KM to CM
        case 8: {
            output_value = (input_value * 100000);
            inputtype="metric";
            break;
        };
        default: {
            alert("Error Occurred :(");
            break;
        };
    };
    switch (output_unit_type) {
        case 1: {
            outputtype="imperial";
            break;
        };
        case 2: {
            outputtype="imperial";
            console.log("2");
            break;
        };
        case 3: {
            outputtype="imperial";
            console.log("3");
            break;
        };
        case 4: {
            outputtype="imperial";
            console.log("4");
            break;
        };
        case 5: {
            outputtype="metric";
            console.log("5");
            break;
        };
        case 6: {
            outputtype="metric";
            console.log("6");
            break;
        };
        case 7: {
            outputtype="metric";
            console.log("7");
            break;
        };
        case 8: {
            outputtype="metric";
            console.log("8");
            break;
        };
        default: {
            alert("Error Occurred :(");
            console.log("9");
            break;
        };
    };
    switch (inputtype) {
        case "metric": {
            //convert input to inches if output is in imperial
            if (outputtype="imperial") {
                output_value /= 2.54;
                //convert input to imperial output
                switch(output_unit_type) {
                    case 1: {
                        output_value /= 12;
                        break;
                    };
                    case 2: {
                        break;
                    };
                    case 3: {
                        output_value /= 36;
                        break;
                    };
                    case 4: {
                        output_value /= 63360;
                        break;
                    };
                }
            } else if (outputtype="metric") {
            //Converting input in centimeters to output with its metric unit
            switch(output_unit_type) {
                case 5: {
                    output_value /= 100;
                    break;
                };
                case 6: {
                    break;
                };
                case 7: {
                    output_value *= 10;
                    break;
                };
                case 8: {
                    output_value /= 1000;
                    break;
                };
            }} else {
                alert("Error Occurred :(")
            }};
//--------------------------------------------------------------------------          
        case "imperial": {
            if  (outputtype = "metric") {
                output_value = (output_value * 2.54);
                //convert input to centimeters
                switch(output_unit_type) {
                        case 5: {
                            output_value = (output_value / 100);
                            break;
                        };
                        case 6: {
                            break;
                        };
                        case 7: {
                            output_value = (output_value * 10);
                            break;
                        };
                        case 8: {
                            output_value = (output_value / 100000);
                            break;
                    };
                }
            } else if (outputtype="imperial") {
            switch(output_unit_type) {
                case 1: {
                    output_value /= 12;
                    break;
                };
                case 2: {
                    break;
                };
                case 3: {
                    output_value /= 36
                    break;
                };
                case 4: {
                    output_value /= 63360;
                    break;
                };
            }} else {
                alert("Error Occurred :(")
            }};          
            }

        };
function test() {
    console.log("testing: " + output_value);
    console.log("testing 2: " + input_value);
    console.log(output_unit_type);
    console.log(input_unit_type);
    console.log("Important: " + outputtype);
    console.log(inputtype);
}

html code:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Metric Converter</title>
    <!--<link rel="stylesheet" href="style.css">-->
</head>
<body>
<main>
<form>
    <h1>Metric Converter</h1>
    <div>
    <h2>Convert From: </h2>
    <p id="error"></p>
    <p id="output"></p>
    <label for="number_input">Input # of units: 
    <input type="number" step="any" title="Please Input numerical values" id="number_input" required></input>
    </label>   
    <fieldset>
    <h3>Imperial</h3>
        <label for="feet1"><input id="feet1" type="radio" name="unitconverting" class="unitconverting" required value=1>Feet</input></label>
        <label for="inch1"><input id="inch1" type="radio" name="unitconverting" class="unitconverting" value=2>Inches</input></label>
        <label for="yard1"><input id="yard1" type="radio" name="unitconverting" class="unitconverting" value=3>Yards</input></label>
        <label for="mile1"><input id="mile1" type="radio" name="unitconverting" class="unitconverting" value=4>Miles</input></label>
    <h3>Metric</h3>
        <label for="meter1"><input id="meter1" type="radio" name="unitconverting" class="unitconverting" required value=5>Meters</input></label>
        <label for="centi1"><input id="centi1" type="radio" name="unitconverting" class="unitconverting" value=6>Centimeters</input></label>
        <label for="milli1"><input id="milli1" type="radio" name="unitconverting" class="unitconverting" value=7>Millimeters</input></label>
        <label for="kilo1"><input id="kilo1" type="radio" name="unitconverting" class="unitconverting" value=8>Kilometers</input></label>
    </fieldset>
        <h2>Convert to:</h2>
        <fieldset>
    <h3>Imperial</h3>
        <label for="feet2"><input id="feet2" type="radio" name="unitconverted" class="unitconverted" required value=1></input>Feet</label>
        <label for="inch2"><input id="inch2" type="radio" name="unitconverted" class="unitconverted" value=2>Inches</input></label>
        <label for="yard2"><input id="yard2" type="radio" name="unitconverted" class="unitconverted" value=3>Yards</input></label>
        <label for="mile2"><input id="mile2" type="radio" name="unitconverted" class="unitconverted" value=4>Miles</input></label>
    <h3>Metric</h3>
        <label for="meter2"><input id="meter2" type="radio" name="unitconverted" class="unitconverted" value=5>Meters</input></label>
        <label for="centi2"><input id="centi2" type="radio" name="unitconverted" class="unitconverted" value=6>Centimeters</input></label>
        <label for="milli2"><input id="milli2" type="radio" name="unitconverted" class="unitconverted" value=7>Millimeters</input></label>
        <label for="kilo2"><input id="kilo2" type="radio" name="unitconverted" class="unitconverted" value=8>Kilometers</input></label>
        </fieldset>
        <button type="button"onclick='convert()'>Convert</button>
        <button type="button"onclick='test()'>Test Button</button>
    </div>
</form>
</main>
    <script src="index.js"></script>
</body>
</html>

I tried everything I could think of.

Stack overflow is trying to tell me that the post is mostly code and I should add more details, but I think I put down everything.
I would like feedback, and also, I’m new to JS and stack overflow, I just made this account just to post this.