Shravya World
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Web product · Finance

Money calculators people can trust, for an India-first finance site

Eighteen calculators - SIP, EMI, PPF, retirement and more - with charts a non-specialist can read, and maths checked against textbook formulas before launch. The checks caught two real errors.

  • 18calculators, each with a chart and a table view
  • 47automated checks against textbook formulas and published figures
  • 2real errors caught before launch

The problem

A finance calculator that is slightly wrong is worse than none: people plan real savings around the number it shows, and nobody re-derives a SIP formula to check it.

The site also had to work for people who are not comfortable with finance jargon, on phones, in Indian number formats - lakhs and crores, not millions.

What we did

  • All the maths lives in one module with no user interface in it, so it can be tested on its own.
  • Every calculator was checked against a published formula or a worked example before its screen was built - including edge cases like zero interest and nonsense inputs.
  • Charts were designed to be readable without the numbers: growth over time, where the money comes from, what an extra payment saves. Each has a table view for screen readers and for anyone who prefers figures.
  • Retirement planning finds the corpus by simulating the actual monthly withdrawals rather than using a shortcut formula.

The result

The checks caught a goal-based SIP that fell ₹40 short of its target through rounding, and a retirement corpus overstated by ₹2.2 crore by a simplified formula. Both were fixed before anyone saw them.

Eighteen calculators are live, from SIP and lump-sum to home-loan prepayment, credit-card payoff, PPF, EPF, SWP, CAGR and an emergency-fund planner.

Built with

Next.jsTypeScriptHand-built SVG chartsAutomated formula tests
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Figures checked against the live product on 21 September 2026.