Compound Interest & Savings Growth Calculator
Calculate how your savings or investment grows over time with compound interest and regular contributions.
Regular amount added each month (optional)
How to Use This Calculator
1. Enter your starting amount — your initial investment or savings balance 2. Add a monthly contribution — regular deposits boost growth significantly 3. Set the interest rate — use 7% for a diversified stock index fund, 4–5% for bonds, 1–2% for savings accounts 4. Choose your time horizon — the longer the period, the more compounding works in your favour 5. Select compounding frequency — most savings accounts and investments compound monthly
The Power of Compounding:
Formula
FV = P(1 + r/n)^(nt) + PMT × [(1 + r/n)^(nt) − 1] / (r/n)Frequently Asked Questions
What interest rate should I use?
For broad stock market index funds, 7% is a commonly used real (inflation-adjusted) long-term average. High-yield savings accounts currently offer 4–5%. Term deposits vary by provider and term.
How often does interest compound?
Most savings accounts compound daily or monthly. Investment returns are typically modelled as monthly. More frequent compounding produces slightly higher returns.
What is the Rule of 72?
Divide 72 by your interest rate to estimate how many years it takes to double your money. At 7%, your money doubles roughly every 10 years (72 ÷ 7 ≈ 10.3).
Does this calculator account for inflation?
No — to account for inflation, subtract the inflation rate from your interest rate. If returns are 9% and inflation is 3%, use 6% for a real return estimate.
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