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Compound Interest Calculator

Online compound interest calculator — periodic contributions, inflation, taxation, chart and annual table, rate comparison

Paramètres
€
%/an
ans
€
%/an
%
Scénarios :
█ Capital initial █ Versements █ Intérêts composés
Évolution du capital
Tableau annuel
Année Capital Versements cumulés Intérêts de l'année Intérêts cumulés Valeur réelle*
* Valeur ajustée à l'inflation
Comparaison de taux
Règle des 72 & Jalons

Intérêts composés : le secret de l'enrichissement à long terme

Les intérêts composés — que Einstein aurait qualifié de « huitième merveille du monde » — sont le phénomène par lequel les intérêts générés par un capital s'ajoutent à ce capital et génèrent à leur tour des intérêts. Plus le temps passe, plus l'effet est spectaculaire.

La formule des intérêts composés

A = P × (1 + r/n)n×t
VariableDéfinition
AMontant final (capital + intérêts)
PCapital principal (mise de départ)
rTaux d'intérêt annuel (ex : 0,07 pour 7%)
nFréquence de capitalisation par an (12 = mensuelle)
tDurée en années

La règle des 72

La règle des 72 est une astuce mentale pour estimer le temps nécessaire pour doubler un capital : divisez 72 par le taux d'intérêt annuel. Exemple : à 6%/an, votre capital double en 72/6 = 12 ans. À 9%, en 8 ans. Plus le taux est élevé, plus le doublement est rapide.

Pourquoi commencer tôt est crucial

Investir 200€/mois pendant 30 ans à 7% génère 3× plus qu'investir 400€/mois pendant 15 ans au même taux, même si les montants totaux versés sont similaires. C'est la force du temps sur les intérêts composés : chaque année supplémentaire a une valeur exponentielle.

Frequently asked questions

With simple interest, only the initial capital generates interest each year. With compound interest, interest is added to the capital and in turn generates inte... With simple interest, only the initial capital generates interest each year. With compound interest, interest is added to the capital and in turn generates interest — it's the snowball effect. Over 20 years at 7%, €10,000 becomes €20,000 with simple interest, but €38,700 with annual compound interest.

Yes, but the marginal effect diminishes. The difference between annual and monthly compounding is significant, but between monthly and daily, the gap becomes ne... Yes, but the marginal effect diminishes. The difference between annual and monthly compounding is significant, but between monthly and daily, the gap becomes negligible. Continuous compounding (e^rt) represents the theoretical maximum. For most investments, monthly frequency is optimal.

Our calculator displays the real inflation-adjusted value in the 'Real value' column of the table and in the result cards. Inflation reduces the purchasing powe... Our calculator displays the real inflation-adjusted value in the 'Real value' column of the table and in the result cards. Inflation reduces the purchasing power of your final capital: at 2% inflation over 20 years, €100 is only worth €67 in today's euros.

The rule of 72 is a mental shortcut: divide 72 by your annual interest rate to get approximately the number of years needed to double your capital. At 8%: 72/8 ... The rule of 72 is a mental shortcut: divide 72 by your annual interest rate to get approximately the number of years needed to double your capital. At 8%: 72/8 = 9 years. At 4%: 72/4 = 18 years. This rule is accurate for rates between 2% and 15%.

The CAGR (Compound Annual Growth Rate) represents the constant fictional annual return rate that would have produced the same final result. It accounts for cont... The CAGR (Compound Annual Growth Rate) represents the constant fictional annual return rate that would have produced the same final result. It accounts for contributions and smooths variations. It is the standard indicator for comparing investments over different time periods.
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