Monthly SIP future value
The SIP page uses FV = P × (((1 + r)^n − 1) ÷ r) × (1 + r), with r as the annual rate divided by 12 and by 100, and n as years times 12.
The rate is an assumption. A fund can return less, and can lose money. The gap between the future value and the cash you paid in is not a promised profit.
One lump sum, compounded
Compound interest uses A = P × (1 + r/n)^(n×t). The n in that formula is compounds per year, not the SIP month count. Use 1 for annual compounding, 4 for quarterly, or 12 for monthly.
The result is the final value, including principal. There is no monthly top-up. If you plan to invest every month, the SIP page is the matching cash flow.
Simple interest stays on the original principal
Simple interest is P × R × T ÷ 100. The result line is the interest, not the maturity amount. Add the principal if you need the total. For the ₹50,000 example, interest is ₹12,000 and the total is ₹62,000.
Do not compare a simple-interest total with a SIP future value and call the larger one “better.” The amounts invested and the timing are different.
Questions
Which page accepts a monthly contribution?
The SIP calculator. Compound interest on this site grows one starting principal.
Does simple interest include the principal in the result?
No. The result is the interest. Add principal for the total.
Are these returns guaranteed?
No. You type the rate. The page only does the arithmetic.