Build a missed-call cost calculator for a local business
Every missed call at a local business is a customer who called a competitor next. Most owners have no idea what that adds up to. In this tutorial you build a small calculator that turns missed calls into a real monthly dollar figure, using nothing but a plain HTML file you can host anywhere.
What you need
You need a text editor and a browser. No accounts, no frameworks, no build tools. If you can save a file and open it, you can finish this.
1Create the calculator file
Create one file called calculator.html. It holds three inputs: missed calls per week, the percent that would book, and your average customer value.
2Write the math in plain JavaScript
Multiply weekly missed calls by 4.33 to get a monthly number, then multiply by the booking percent and your average customer value.
3Serve it locally to test
Run one zero-config command, python3 -m http.server, then open the page in your browser.
4Enter real numbers
Fifteen missed calls a week at a 30 percent booking rate and a 200 dollar customer value comes out to 3897 dollars a month walking out the door.
5Confirm it works on mobile
Resize your browser to a phone width and confirm the card still reads cleanly. Local business owners will open this on their phone.
What can go wrong
The most common mistake is forgetting to convert the weekly number to monthly, which makes the total look four times too small. The second is treating the percent as a decimal already. Keep it as a whole number and divide by 100 in the code.
Knowledge check
0/3 correct1. How do you turn weekly missed calls into a monthly number?
2. If a shop misses 15 calls a week, books 30 percent, and each customer is worth 200 dollars, what is the rough monthly loss?
3. Why keep the booking percent as a whole number in the code?