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How to Create a Simple Calculator Using HTML and JavaScript

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Here are the steps to create a simple calculator using HTML and JavaScript which can evaluate simple arithmetic on integer numbers. Two types of inputs text and button are used here on a table within a form element and the OnClick event was used to insert button values on the screen or to evaluate the numbers.

Steps to create a Simple calculator Using HTML and JavaScript

1. At first Insert a <form> element within <body> tag.
2. Create a table using <table> …..</table> tag.
3. Insert two types of Input text and button within table data of table row using <tr><td>….</td></tr> tag.
4. Assign OnClick event for all the buttons having numbers and arithmetic operators.
5. Give blank value for Clear(C) button.
6. Use eval() function to evaluate the numbers on OnClick event of equal to sign button.

Full HTML code for a Simple HTML calculator

<html><head></head><body><h3>Simple Calculator</h3><br/><style>#calc{width:300px;height:250px;}
#btn{width:100%;height:40px;font-size:20px;}
</style><form Name="calc"><table id="calc" border=2><tr><td colspan=5><input id="btn" name="display" onkeypress="return event.charCode >= 48 && event.charCode <= 57" type="text"></td><td style="display:none"><input name="M" type="number"></td></tr><tr><td><input id="btn" type=button value="MC" OnClick="calc.M.value=''"></td><td><input id="btn" type=button value="0" OnClick="calc.display.value+='0'"></td><td><input id="btn" type=button value="1" OnClick="calc.display.value+='1'"></td><td><input id="btn" type=button value="2" OnClick="calc.display.value+='2'"></td><td><input id="btn" type=button value="+" OnClick="calc.display.value+='+'"></td></tr><tr><td><input id="btn" type=button value="MS" OnClick="calc.M.value=calc.display.value"></td><td><input id="btn" type=button value="3" OnClick="calc.display.value+='3'"></td><td><input id="btn" type=button value="4" OnClick="calc.display.value+='4'"></td><td><input id="btn" type=button value="5" OnClick="calc.display.value+='5'"></td><td><input id="btn" type=button value="-" OnClick="calc.display.value+='-'"></td></tr><tr><td><input id="btn" type=button value="MR" OnClick="calc.display.value=calc.M.value"></td><td><input id="btn" type=button value="6" OnClick="calc.display.value+='6'"></td><td><input id="btn" type=button value="7" OnClick="calc.display.value+='7'"></td><td><input id="btn" type=button value="8" OnClick="calc.display.value+='8'"></td><td><input id="btn" type=button value="x" OnClick="calc.display.value+='*'"></td></tr><tr><td><input id="btn" type=button value="M+" OnClick="calc.M.value=(Number(calc.M.value))+(Number(calc.display.value))"></td><td><input id="btn" type=button value="9" OnClick="calc.display.value+='9'"></td><td><input id="btn" type=button value="±" OnClick="calc.display.value=(calc.display.value==Math.abs(calc.display.value)?-(calc.display.value):Math.abs(calc.display.value))"></td><td><input id="btn" type=button value="=" OnClick="calc.display.value=eval(calc.display.value)"></td><td><input id="btn" type=button value="/" OnClick="calc.display.value+='/'"></td></tr><tr><td><input id="btn" type=button value="1/x" OnClick="calc.display.value=1/calc.display.value"></td><td><input id="btn" type=button value="." OnClick="calc.display.value+='.'"></td><td><input id="btn" type=button value="x2" OnClick="calc.display.value=Math.pow(calc.display.value,2)"></td><td><input id="btn" type=button value="√" OnClick="calc.display.value=Math.sqrt(calc.display.value)"></td><td><input id="btn" type=button value="C" OnClick="calc.display.value=''"></td></tr></table></form></body></html>

Preview of Simple HTML calculator

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Shuseel Baral is a web programmer and the founder of InfoTechSite has over 8 years of experience in software development, internet, SEO, blogging and marketing digital products and services is passionate about exceeding your expectations.

3 Comments

  1. shuseel
    Please tell me how to design two inputs type=text that the question appear in the first input
    and the result appear in the second one?

  2. Very useful material added to his bookmarks. I tried many different services for creating online calculators, among which Contact Form 7 and uCalc plugin were the most popular. Pretty good tools for creating calculators.

  3. garbageoverflowReply

    Dear people,
    I made a caluclator app in HTML CSS and JS, it’s basically a .hta file.
    I made a github repo, if it helps. The app looks nice and has hover effects, if the design doesn’t fir you, you can
    also customize it with css.

    No problem if you don’t know how to customize it, we even have a guide in the README.md file, that helps
    you to customize the app.

    Visit the github repo here github.com/garbageoverflow/calculator

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