Fast, transparent, open calculations
Practical tools for investors who want clearer decisions.
Run compound growth, DCA, ROI, rent-vs-buy, FIRE, mortgage payoff, and real estate investment scenarios in seconds. No sign-ups. No fluff.
Ten tools. Zero guesswork.
Each calculator runs instantly in your browser using standard financial formulas. No account required. Export to PDF or share via URL.
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.
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.
Inflation / Future Value
Understand how inflation erodes purchasing power and what future amounts you will need to maintain today's value.
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.
Savings Goal
Enter a target amount and timeline, get the monthly savings needed at various return rates to hit your number.
Mortgage Payoff
Model extra payments on a mortgage and see how much time and interest you save by paying ahead of schedule.
FIRE Calculator
Financial Independence, Retire Early — enter your income, savings rate, and expenses to see when you hit your number.
Calculator Workspace
Inputs
Results
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
Your Numbers
FIRE Analysis
Compare Scenarios
Run two scenarios side by side to see how different assumptions change outcomes.
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.