# $100,000 at 8% for 20 Years — Compound Interest Calculator

> See how $100,000 grows to $492,680 in 20 years at 8% compounded monthly — a 4.9× return, typical of a long-run equity portfolio.

- **Answer:** ~$492,680
- **Category:** Finance & Money
- **Interactive calculator:** https://youcalc.com/en/finance-money/compound-interest/100k-at-8pct-20-years/
- **Price:** Free, no sign-up required
- **Full calculator:** [Compound Interest Calculator](https://youcalc.com/en/finance-money/compound-interest/)
- **Pre-filled inputs:** `p=100000&r=8&y=20&n=12&c=USD`

| Metric | Value |
| --- | --- |
| Final balance | $492,680 |
| Starting principal | $100,000 |
| Total interest earned | $392,680 |
| Total contributed | $0 |
| Growth multiplier | 4.93× |


## Overview

An $100,000 lump sum at a steady 8% annual return — roughly the historical S&P 500 average — becomes nearly half a million dollars in 20 years without a single extra dollar invested. The interest earned ($392,680) is nearly four times the principal. Compare this with the 7%/20-year scenario to see how one extra percentage point adds about $92,000.

## Method

The future value uses the standard compound-interest formula A = P(1 + r/n)^(nt) combined with the future value of a recurring contribution. P is the starting principal, r the annual rate, n the number of compounding periods per year, and t the number of years. Contributions are applied at the start or end of each period depending on your selection.

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- [Retirement Savings Calculator](https://youcalc.com/en/finance-money/retirement-savings/)
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## Sources

- https://www.investor.gov/financial-tools-calculators/calculators/compound-interest-calculator
- https://www.investopedia.com/terms/c/compoundinterest.asp
- https://www.nerdwallet.com/calculator/compound-interest-calculator

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Interactive version: https://youcalc.com/en/finance-money/compound-interest/100k-at-8pct-20-years/ · From YouCalc — https://youcalc.com