WebTools is a small set of free calculators I’m building for everyday money questions in India. Most calculator sites give you a number and little else. I wanted tools that show their assumptions, explain the formula in plain English, and let you check the answer yourself.
The first tool: a SIP calculator
The SIP calculator answers three questions: what a monthly SIP could grow to, what SIP a goal needs, and how long a goal could take. It handles yearly step-ups, a starting lumpsum, start- or end-of-month investing and inflation, and it shows every result with the assumptions behind it. You can try “what if” changes, compare returns 2 points higher or lower, and download the year-by-year table.
How I build it
- Tested maths. The formulas live in small, pure functions, checked against values I worked out separately in Python, so the page and the tests can’t quietly agree on a wrong answer.
- Explained visually. Each page walks through one example with step cards, bars and a worked “receipt” instead of long paragraphs.
- Private by default. Calculations run in your browser. What you type is never sent anywhere; anonymous usage analytics only record which parts of the page people use.
- Fast and accessible. It’s a static site on Cloudflare, works in light and dark mode, and is tested for keyboard and screen-reader use.
It’s an educational project, not financial advice. More calculators are on the way, each one added only once its maths and explanations are tested.