Why We Built CoastVest

Every compound interest calculator we found treated investing as a single, continuous timeline. You enter a starting amount, a monthly contribution, and a number of years — and the calculator shows you a final value. Simple, but incomplete.

The problem is that real investing has two distinct phases: a contribution phase where you actively add money each month, and an invested phase where you stop contributing but let compound growth continue. Treating these as the same thing hides one of the most powerful insights in personal finance: your money keeps growing long after you stop adding to it.

CoastVest was built to model both phases separately, clearly, and visually. Enter how long you plan to contribute. Enter how many additional years your money will grow after that. See exactly where you stand — your coast number, your final value, and the dramatic visual difference between the amount you invested and the amount compound interest delivers.

What We Believe

Financial tools should be free, honest, and private. All calculations on CoastVest run entirely in your browser — your financial data never leaves your device and is never stored on any server. There are no accounts, no signups, and no upsells. The calculators are free because financial clarity shouldn't cost money.

We believe in transparent math. Every formula used in our calculators is documented and explainable. If you want to know how a number was calculated, you should be able to find out.

A Note on Financial Advice

CoastVest is an educational tool. The calculators model mathematical scenarios based on inputs you provide and assumed constant rates of return. Real markets are more complex — returns vary year to year, inflation erodes purchasing power, and tax situations differ for every person.

Nothing on CoastVest constitutes financial advice. For decisions about your actual retirement savings, tax strategy, or investment allocation, please consult a qualified financial advisor. Our full disclaimer is here.