Fast, transparent, open calculations
Practical tools for investors who want clearer decisions.
Run compound growth, DCA, ROI, rent-vs-buy, FIRE, retirement withdrawal, dividend, fee, mortgage payoff, and real estate scenarios in seconds. No sign-ups. No fluff.
Thirteen tools. Zero guesswork.
Each calculator runs instantly in your browser using standard financial formulas. No account required. Export to PDF or share via URL.
Grow Model how money compounds, what it costs, and what it pays.
Compound Interest
See how initial capital, regular contributions, and time combine to grow your wealth through compounding.
Dollar-Cost Averaging
Model the impact of consistent weekly or monthly contributions over time, regardless of market timing.
ROI Calculator
Calculate total return, percentage gain, and annualized return for any investment over a defined period.
Rule of 72 / 69
Quickly estimate how long it takes to double your money at a given rate using the Rule of 72 or the more precise Rule of 69.
Inflation / Future Value
Understand how inflation erodes purchasing power and what future amounts you will need to maintain today's value.
Fee Impact
Compare two expense ratios and see how much a seemingly small fee costs you over decades of compounding.
Dividend Income
Project your future dividend income with yield, dividend growth, ongoing contributions, and reinvestment (DRIP).
Plan Work backward from a goal, an early retirement, or a drawdown.
Savings Goal
Enter a target amount and timeline, get the monthly savings needed at various return rates to hit your number.
FIRE Calculator
Financial Independence, Retire Early — enter your income, savings rate, and expenses to see when you hit your number.
Retirement Withdrawal
See how long your portfolio lasts with inflation-adjusted withdrawals, and the most you can safely spend each year.
Property Price a rental, weigh renting against buying, and pay down debt.
Real Estate Investment
Analyze purchase price, financing, rental income, expenses, appreciation, and projected profit over a hold period.
Rent vs Buy
Compare the total cost of homeownership against renting under your specific assumptions and timeline.
Mortgage Payoff
Model extra payments on a mortgage and see how much time and interest you save by paying ahead of schedule.
Calculator Workspace
Inputs
Results
Year-by-year breakdown
Inputs
Results
Inputs
Results
Property & Financing
Investment Analysis
Assumptions
Comparison
Inputs
Results
Inputs
Time to Double
Inputs
Monthly Savings Needed
At Different Return Rates
Loan Details
Payoff Analysis
Amortization schedule (yearly)
Your Numbers
Use a real (after-inflation) return, such as 5–7%, so every figure stays in today's dollars.
FIRE Analysis
Retirement Plan
Drawdown Analysis
Inputs
Income Projection
Inputs
Fee Drag
Compare Scenarios
Run two scenarios side by side. Scenario B shows how far each result moves from Scenario A.
Scenario A
Scenario B
Key Assumptions Reference
Historical averages to help you choose realistic inputs. All figures are nominal unless noted.
Stock Market Returns (S&P 500)
| Period | Annualized Return | With Dividends |
|---|---|---|
| 1926 – 2024 | 10.3% | ~12% |
| 1990 – 2024 | 10.5% | ~12.2% |
| 2000 – 2024 | 7.5% | ~9.8% |
| 2010 – 2024 | 13.0% | ~15.2% |
| Real return (inflation-adj) | ~7% long-term average | |
Inflation (U.S. CPI)
| Period | Average Annual |
|---|---|
| 1926 – 2024 | 2.9% |
| 1990 – 2024 | 2.6% |
| 2000 – 2024 | 2.5% |
| 2020 – 2024 | 4.9% |
| Fed target | 2.0% |
Mortgage Rates (30-Year Fixed)
| Period | Average Rate |
|---|---|
| 1971 – 2024 | 7.7% |
| 2000 – 2024 | 5.1% |
| 2010 – 2020 | 4.0% |
| 2021 – 2024 | 5.8% |
| Current (2025) | ~6.5 – 7.0% |
Real Estate Appreciation
| Period | Annualized |
|---|---|
| 1991 – 2024 (Case-Shiller) | 4.6% |
| 2000 – 2024 | 4.8% |
| 2010 – 2024 | 6.8% |
| Real return (inflation-adj) | ~1.5 – 2% |
| Conservative planning input | 2 – 3% |
Why Investment.tools
Fast, transparent calculators
Every calculation runs instantly in your browser using standard financial formulas. No hidden assumptions, no black boxes, no server round-trips.
Practical scenarios, not fluff
Built for real decisions — property acquisitions, portfolio growth, rent-vs-buy tradeoffs, FIRE planning, and mortgage payoff strategy.
Built for real-world decisions
No sign-ups, no paywalls, no data collection. Share scenarios via URL, export to PDF, or compare two scenarios side by side.
Methodology
How these tools work, what they assume, and what they cannot tell you.
Assumptions shape outcomes
Every calculator produces results based entirely on the inputs you provide. A 1% change in expected return or a 5-year change in time horizon can shift results by tens of thousands of dollars. Always run multiple scenarios — optimistic, realistic, and conservative — to understand the range of outcomes.
Calculators are scenario tools
These tools model hypothetical outcomes under constant assumptions. Real markets fluctuate, tax laws change, expenses surprise you, and life rarely follows a straight line. Use calculators to build intuition and compare options — not to predict the future with precision.
Compounding, inflation, and risk
Compounding accelerates growth over time, but inflation erodes it. Risk means your actual path will look nothing like a smooth curve. The longer your time horizon, the more compounding works in your favor, but only if you stay invested through volatility.
Frequently Asked Questions
Our calculators use standard financial formulas and produce mathematically precise results based on the assumptions you enter. Real-world outcomes will differ because markets, interest rates, taxes, and fees change over time. Use these as scenario-planning tools, not as guarantees.
No. Investment.tools provides informational calculators only and does not provide financial, tax, or investment advice. Results are based entirely on user-entered assumptions and should not be used as the sole basis for any financial decision.
Each calculator uses the inputs you provide — return rates, time horizons, contribution amounts, and other variables. The projections assume constant rates and consistent contributions, which rarely match real-world conditions exactly. Adjust inputs freely to model different scenarios.
Use calculators to compare scenarios, not to predict outcomes. Run multiple inputs — optimistic, realistic, and conservative — to understand the range of possible results. Pay special attention to how small changes in assumptions create large differences in outcomes.
Yes. Use the Real Estate Investment Calculator to model property returns, then compare those outputs against the Compound Interest or DCA calculators. Better yet, use the Comparison Mode to run two scenarios side by side.
Markets are inherently volatile. Annual returns in stocks have historically ranged from roughly -37% to +50% in any given year, even though long-term averages hover around 7-10%. Compounding amplifies both gains and losses, which is why time horizon and consistency matter more than any single year's performance.
The widely cited 4% rule says withdrawing 4% of your portfolio in year one, then adjusting for inflation, has historically lasted about 30 years for a balanced portfolio. It is a rule of thumb, not a guarantee — longer retirements, high fees, or poor early returns call for a lower rate. Use the Retirement Withdrawal Calculator to test your own numbers.
More than they appear. Because a fee is charged on your whole balance every year, its cost compounds. Over 30 years, a 1% annual fee can reduce your ending balance by roughly 20-25% compared with a low-cost index fund. The Fee Impact Calculator shows the exact difference for your inputs.