Compound Interest Calculator

Compound interest is often called the eighth wonder of the world. The concept is deceptively simple: you earn interest not only on your original principal, but also on the interest that has already accumulated. Over time, this creates an exponential growth curve that accelerates the longer you stay invested.

For example, $10,000 invested at 10% annual return grows to $25,937 in 10 years, $67,275 in 20 years, and $174,494 in 30 years. Notice how the growth in the final decade ($107,219) is far larger than the first decade ($15,937). This is the compounding snowball in action.

Simple interest is calculated only on the original principal. A $10,000 investment at 10% simple interest earns exactly $1,000 per year, regardless of how long you hold it. After 10 years, you have $20,000.

Compound interest reinvests your earnings. That same $10,000 at 10% compounded annually becomes $25,937 after 10 years — an extra $5,937 from compounding alone. The higher the rate and the longer the period, the more dramatic the difference.

The more frequently interest compounds, the faster your money grows. With the same nominal rate, daily compounding beats monthly, which beats quarterly, which beats annually. The difference is modest at low rates but becomes significant at higher rates common in crypto staking and DeFi.

In DeFi protocols where auto-compounders run multiple times per day, the effective yield can be noticeably higher than the advertised APR, especially at rates above 20%.

Traditional investments like index funds historically return 7-10% annually. Crypto staking yields vary widely: Ethereum staking offers 3-5%, Solana 6-8%, while DeFi liquidity pools can exceed 20-100%+. However, higher returns in crypto come with additional risks.

Price volatility is the biggest differentiator. A 12% staking yield means little if the underlying token drops 40%. Traditional investments offer more stable principal value, making compound growth more predictable. When modeling crypto staking returns, remember that your actual USD value depends on both the staking yield and the token price.

The Rule of 72 provides a quick mental estimate for how long it takes your money to double. Simply divide 72 by your annual interest rate. At 8%, your money doubles in approximately 9 years (72 / 8 = 9). At 12%, it doubles in 6 years. At 20%, just 3.6 years.

This rule is most accurate for rates between 6% and 10%, but works as a reasonable approximation for a wider range. It highlights why even small differences in rate matter enormously over long time horizons.

Adding regular monthly contributions (dollar-cost averaging) to a compounding investment creates a powerful wealth-building engine. Each contribution begins its own compounding journey. Your first month's contribution compounds for the entire investment period, while your last contribution barely compounds at all.

This is why starting early matters more than contributing more later. A $500/month contribution over 20 years at 10% grows to approximately $380,000 — you contributed $120,000, but earned $260,000 in interest. The same $500/month over only 10 years yields about $103,000, demonstrating how the final years of a long investment contribute disproportionately to total growth.