Finance

Compound Interest Calculator

Project how a starting amount and optional monthly contributions grow over time under compound interest. Choose the compounding frequency — from daily to continuous — and see the year-by-year balance, total contributions, and interest earned.

Résumé de l'outil

Cet outil accepte une entrée structurée et renvoie une sortie déterministe dans le navigateur, sans envoi au serveur.

Nom de l'outil: Compound Interest Calculator
Intention d'entrée: Fournissez le contenu source à transformer, valider ou analyser.
Intention de sortie: Recevez une sortie normalisée prête à être copiée, réutilisée ou déboguée.
Entrée d'exemple: $10,000 · 7% · 20 years · monthly · no contributions
Sortie d'exemple: Future value ≈ $40,387 · Interest ≈ $30,387

Starting amount

CurrencyAnnual interest rate (%)YearsCompoundingMonthly contribution (optional)

Future value

$20,096.61

Contributions

$10,000.00

Interest earned

$10,096.61

Year	Contributions	Interest	Balance
Year 1	$10,000.00	$722.90	$10,722.90
Year 2	$10,000.00	$1,498.06	$11,498.06
Year 3	$10,000.00	$2,329.26	$12,329.26
Year 4	$10,000.00	$3,220.54	$13,220.54
Year 5	$10,000.00	$4,176.25	$14,176.25
Year 6	$10,000.00	$5,201.06	$15,201.06
Year 7	$10,000.00	$6,299.94	$16,299.94
Year 8	$10,000.00	$7,478.26	$17,478.26
Year 9	$10,000.00	$8,741.77	$18,741.77
Year 10	$10,000.00	$10,096.61	$20,096.61

Uses the compound interest formula A = P(1 + r/n)^(nt) — or A = Pe^(rt) for continuous compounding — with monthly contributions distributed across periods. Investment returns vary; this is a deterministic projection, not a guarantee.

Introduction à l'outil

Vue d'ensemble de l'outil

Compound interest is interest that earns interest: each period, the balance is multiplied by 1 + r/n (or e^(r/n) in the continuous limit), so growth is exponential rather than linear. This calculator treats principal plus optional regular contributions the same way a savings account, fixed deposit, SIP, or index-fund projection would. Results are deterministic — real investment returns fluctuate — so treat the output as a planning estimate, not a guarantee.

Cas d'usage

Plan a retirement, emergency-fund, or down-payment target
Compare a lump-sum investment to a systematic monthly plan
Estimate future value of a fixed deposit or index fund
Quantify how compounding frequency changes the final balance

Exemples d'entrée/sortie

Intention d'entrée

$10,000 · 7% · 20 years · monthly · no contributions

Intention de sortie

Future value ≈ $40,387 · Interest ≈ $30,387

Intention d'entrée

$0 · 8% · 30 years · monthly · $500/month

Intention de sortie

Future value ≈ $745,180 · Contributions $180,000 · Interest ≈ $565,180

Questions fréquentes

What is the compound interest formula?+

A = P · (1 + r/n)^(n·t), where P is principal, r is the annual rate, n is the number of compounding periods per year, and t is time in years. For continuous compounding the formula is A = P · e^(r·t).

How are monthly contributions handled?+

Contributions are converted to a per-period amount (for example, $500/month becomes $1,500/quarter when compounding is quarterly) and added at the end of each period before the next compounding step.

Is this a SIP (Systematic Investment Plan) calculator?+

Yes — use the monthly-contribution field and pick monthly compounding to model a typical SIP at an assumed annualized return.

Does compounding frequency matter much?+

At typical savings rates the difference between daily and continuous compounding is small, but over long horizons or higher rates it is noticeable. Try the same inputs across frequencies to see the gap.