Why two calculators disagree, where a formula comes from, and which convention a number was computed under. https://numera.tools/in/feed.xml 2026-08-19T00:00:00Z https://numera.tools/in/blog/why-two-sip-calculators-disagree/ 2026-08-19T00:00:00Z 2026-08-19T00:00:00Z Ravi Teja

On ₹10,000 a month for ten years at 12%, the two conventions in common use give ₹23,23,391 and ₹23,00,387. The gap of ₹23,004 is one extra month of compounding on every instalment, and it comes from whether the calculator assumes you invest at the start of the month or at the end.

https://numera.tools/in/blog/flat-rate-versus-reducing-balance/ 2026-08-19T00:00:00Z 2026-08-19T00:00:00Z Ravi Teja

On ₹5,00,000 over five years, a 10% flat rate produces an EMI of ₹12,500 and total interest of ₹2,50,000. The same repayments on a reducing balance basis correspond to a rate of 17.27%. Flat rate understates the true cost by 7.27 percentage points here.

https://numera.tools/in/blog/lakh-crore-and-the-3-2-2-grouping/ 2026-08-19T00:00:00Z 2026-08-19T00:00:00Z Ravi Teja

One crore is 10,000,000, written 1,00,00,000 in Indian grouping. The Indian system groups the first three digits then two at a time; the international system groups three throughout. One crore is ten million and one lakh is a hundred thousand, but there is no single word for a million in the Indian system and none for a lakh in the international one.

https://numera.tools/in/blog/the-emi-formula-in-plain-english/ 2026-08-19T00:00:00Z 2026-08-19T00:00:00Z Ravi Teja

EMI = P × i × (1+i)^n / ((1+i)^n − 1), where P is the amount borrowed, i is the monthly rate and n is the number of instalments. On ₹50,00,000 at 8.5% over 20 years that gives ₹43,391 a month. In a spreadsheet it is PMT(8.5%/12, 240, -5000000).