About Grow My Interest

Grow My Interest is one tool: a compound interest calculator that turns an initial deposit, an optional regular contribution, an interest rate and a compounding frequency into a final balance, total interest, effective annual yield, a year-by-year table and a growth chart. It launches as a single page on purpose -- one calculator, done well, rather than a hub of thin ones.

The formulas it uses

Standard, published compound-interest algebra: A = P(1 + r/n)ⁿᵗ for a lump sum, P·eʳᵗ in the limit of continuous compounding, and the ordinary/annuity-due future-value formulas for a regular contribution added at the end or start of each period. Annual Percentage Yield follows APY = (1 + r/n)ⁿ − 1. None of this is original research -- it's the same math a textbook, a bank's disclosure, or the U.S. government's own investor.gov calculator uses. The full derivation and a worked example are on the calculator page itself.

What it doesn't do

It doesn't know your tax bracket, account type, or your bank's exact crediting schedule, and it assumes a constant rate and a constant contribution amount for the whole term (aside from the optional annual step-up you can turn on). It isn't investment, tax or financial advice -- see Terms.

What's coming

If this calculator earns real traffic, the plan is to expand into the closely related questions people search for around it, each as its own page rather than folded into this one:

• Compound Interest Formula -- the algebra behind A = P(1+r/n)ⁿᵗ, solved for each variable.
• Compounding Calculator -- compare compounding frequencies side by side at a glance.
• Daily Compound Interest Calculator -- day-by-day accrual, the way many high-yield savings accounts actually credit interest.
• Compound Growth Calculator -- the same math applied beyond interest-bearing accounts.
• 401(k) Compound Interest Calculator -- payroll contributions, employer match, and a multi-decade horizon.
• CD Monthly Interest Calculator -- fixed-term certificates of deposit with monthly crediting.

Until then, this one page is the whole site.

Corrections

If a formula or number here is wrong, email hello@growmyinterest.com.