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🧮 Simple Interest Calculator
Calculate simple interest (SI = P × R × T) and total amount payable

A Simple Interest of ₹1,00,000 for 5 years at 8% is ₹1.40 L.

Formula

Simple Interest = (Principal × Rate × Time) ÷ 100; Total Amount = Principal + Simple Interest

Worked example
InputValue
Principal Amount₹1,00,000
Annual Interest Rate8%
Time Period5 yr
Total Amount₹1,40,000
Simple Interest₹40,000
Principal₹1,00,000

Simple interest — and where it still applies

Simple interest pays only on the original principal — the interest never joins the base. SI = P × R × T: linear, predictable, and always smaller than compound growthEarning returns on your returns — growth that accelerates over time. over multi-year periods. It survives mostly in informal lending, some bondsA loan to a government or company that pays fixed interest.’ coupon quotes, penalty/late-fee calculations, and short-tenure loans.

Example₹2 lakh lent at 12% simple for 5 years: interest = 2,00,000 × 0.12 × 5 = ₹1.2 lakh, total ₹3.2 lakh. Compounded annually, the same deal returns ₹3.52 lakh — ₹32,000 more, purely from interest earning interest. The longer the tenure, the wider the gapA jump between one bar’s close and the next bar’s open.: by year 20 it’s ₹4.8 lakh vs ₹9.6 lakh of interest — double.
The practical use of this calculator is decoding informal-market quotes: “2 rupees per hundred per month” — a common moneylender rate — is 2% monthly simple ≈ 24% a year, and effectively more if fees are deducted upfront. Converting every quoted rate to an annual percentage before agreeing is the single best defence against expensive informal credit.
Common mistakeAssuming a quoted rate is comparable across products: banks compound deposits quarterly, bondsA loan to a government or company that pays fixed interest. may pay simple coupons, informal lenders quote monthly — an “identical 12%” can differ by whole percentage points in effect. Always convert to the effective annual rate (this tool and the compound calculator together do it) before comparing.
✓ You learnedSimple interest is linear (P × R × T) and always loses to compoundingEarning returns on your returns — growth that accelerates over time. over time — fine for short tenures, costly to confuse with compound quotes. Convert every informal or monthly rate to effective annual terms before you borrow or lend a rupee.
FAQs
Where is simple interest actually used in India?

Late-payment penalties and statutory interest (often quoted as simple), some corporate FD and bond coupon structures, gold-loan and informal lending quotes, and education-loan simple-interest periods during moratorium at some lenders. Bank deposits and loans otherwise compound — assume compounding unless a document explicitly says simple.