Loan Calculator — EMI & Amortization

Most of what you repay on a 30-year mortgage is interest, and the number that reveals it is not the monthly payment. The Loan Calculator works out the instalment from amount, rate and term, then shows the total interest beside it, splits every payment into principal and interest, and tells you what an extra 100 a month would save.

The instalment comes from the standard amortization formula that banks use, so the figure matches a real loan agreement rather than approximating it. A 0% loan is handled separately, since that expression divides by zero, and an interest-free plan is simply the principal split evenly across the term.

Ten currency symbols are offered, from USD and EUR through INR, BDT and NGN. None of them changes the arithmetic, which is currency-agnostic and involves no exchange rates or live data. Nothing you type about your finances leaves the page.

Worked Example: A 30-Year Mortgage

Tap the Mortgage sample chip for 320,000 at 6.25% over 30 years. The instalment is $1,970.30, the total repaid is $709,306.21, and the interest alone is $389,306.21. That is 54.9% of everything you hand over, which the split bar draws as a single image. Now put 200into Extra Monthly Payment: the loan clears in 282 instalments instead of 360, 6 and a half years early, and the interest saved is $99,019.50 for an outlay of 200 a month.

The Controls Worth Finding

• Loan Term toggles between Yrs and Mos, because lenders quote a car loan in months and a mortgage in years, and converting by hand is where errors creep in.
• First Payment Month turns the schedule's period numbers into real calendar months and gives you an actual payoff date rather than a count.
• The Amortization Schedule hides behind a Show button. Inside it, a Monthly and Yearly switch collapses 360 rows into 30, and a CSV button copies the whole table for a spreadsheet.
• Four sample chips cover a car, a mortgage, a student loan and a personal loan, the last of which arrives with an extra payment already set so the comparison is visible immediately.
• Thousands separators are stripped on the way in, so 320,000 pasted straight from a quote parses without editing.

Accuracy and Where the Model Stops

• The term is capped at 600 months, which is 50 years. Beyond that you get Loan term cannot exceed 50 years (600 months)., a limit that also keeps the schedule table from freezing the tab.
• Rates above 100% are refused with Interest rate must be 100% or lower., and a negative extra payment or a zero principal are each rejected with their own message.
• Interest is compounded monthly at one twelfth of the annual rate. Lenders quoting an APR that includes fees, or compounding daily, will differ slightly from the figure here.
• Fees, insurance, taxes and early-repayment penalties are not modelled. On a mortgage those can add a substantial amount to what actually leaves your account each month.
• The extra payment is assumed to be made every month from the first instalment onwards. A lump sum in year 5 saves a different amount, and this model will overstate it.
• Every balance is carried at full precision and only rounded for display, so the closing balance reaches exactly zero rather than drifting by a few cents across 360 rows.