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This tool is part of these guided projects. Each project provides step-by-step instructions with checklists and all the tools you need in one place.
Build a personal or household budget with clear income tracking, expense categories, and savings goals.
Assess your finances, set retirement goals, calculate savings needed, and build an investment strategy with automatic contributions.
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Calculate simple interest on loans or investments. Principal × rate × time. Quick and straightforward calculation. Free online calculator with instant
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Calculate Return on Investment. Gain divided by cost. Get ROI percentage and net profit. Essential for business decisions.
Compound interest calculates returns on both the initial principal and accumulated interest from previous periods.
A = P(1 + r/n)^(nt) where P = principal, r = annual rate, n = compounds per year, t = yearsA quick mental math shortcut to estimate how long it takes for an investment to double at a given interest rate.
Years to double ≈ 72 / interest rate (%)The Compound Interest Calculator applies industry-standard financial equations used by lenders, accountants, and planners. All intermediate values are computed with floating-point precision and rounded only for display.
Result = f(principal, rate, period, …)Updated: July 2026
$10,000 initial deposit plus $500/month contributions at 7% annual return over 30 years.
→ Future value: $611,000+
$30,000 loan at 5% compounded monthly — see total cost over 10 years.
→ Total amount grows significantly due to compounding
A homebuyer runs the Compound Interest Calculator with two interest rates side by side to compare total interest paid over 30 years before choosing a lender.
Compound interest grows exponentially faster because you earn returns on previous returns. Simple interest only applies to the original principal.
Real returns = nominal returns minus inflation rate. A 7% return with 3% inflation means your purchasing power grows at roughly 4% per year.
See how your money grows when interest earns interest over time. Enter your starting balance, annual rate, compounding frequency, and time horizon to project future value for savings accounts, investments, and retirement planning.