Pounds-to-tons converter
The label element can be used for the labels of the input fields.

The placeholder attribute shouldn’t be used for labeling.

The output element can be used for the result. (You are using a label, which is not appropriate; and note that label can’t have a type attribute.)

Maybe a button with the button type is more appropriate here. (Button type “button” vs. “submit”)

This results in:

&lt;label for="loaded"&gt;Loaded pounds&lt;/label&gt;
&lt;input type="number" id="loaded"&gt;

&lt;label for="unloaded"&gt;Unloaded pounds&lt;/label&gt;
&lt;input type="number" id="unloaded"&gt;

&lt;button type="button" id="button" onclick="calc()"&gt;Convert&lt;/button&gt;

&lt;output for="loaded unloaded" id="result"&gt;&lt;/output&gt;