Financial Guides & Resources
Clear, in-depth guides that explain the ideas behind every number our calculators produce — from compound interest and the Rule of 72 to retirement targets, emergency funds and financial independence.
A calculator gives you an answer in seconds, but the answer only matters if you understand the question behind it. That is what this learning hub is for. Every guide here takes a single financial idea — how money compounds, how much you really need to retire, why an emergency fund changes everything — and explains it from first principles, with worked examples and practical steps you can act on today.
The guides and the tools are designed to work together. Read a guide to build the intuition, then jump straight into the matching calculator to run your own numbers. Start with the fundamentals in how compound interest works, or head directly to the free compound interest calculator if you already know the theory and just want to model your plan.
The Library
All Financial Guides
Every guide is original, in-depth and written to stand on its own. Pick a topic below.
How Does Compound Interest Work?
The formula, the intuition and the examples behind exponential growth — and why starting early beats investing more.
Read guide →How to Calculate Future Value
The future value formula step by step — lump sums, monthly contributions, inflation and real planning examples.
Read guide →How Much Should You Invest Every Month?
How much experts recommend by age and income, the 15% rule, and why consistency beats timing.
Read guide →How to Reach Your Savings Goals Faster
Set targets, automate deposits, use high-yield accounts and budget smarter to hit any goal sooner.
Read guide →What Is the Rule of 72?
The mental shortcut that tells you how long money takes to double — where it comes from, when it is accurate, and how to use it.
Read guide →How Much Money Do You Need To Retire?
The 25x rule, the 4% withdrawal guideline and a step-by-step method to turn your spending into a concrete savings target.
Read guide →How Much Emergency Fund Do You Need?
How to size, build and store the cash buffer that keeps a bad month from becoming a financial disaster.
Read guide →What Is FIRE (Financial Independence, Retire Early)?
The movement, the math and the variations — Lean, Fat, Barista and Coast FIRE — plus how to find your own number.
Read guide →Category
Investing & Growth
How money grows over time, and the simple math that explains it. Read the guide, then model it with the matching calculator.
How Does Compound Interest Work?
Build the intuition, then run the numbers on the Investment Growth and Future Value calculators.
Read guide →How to Calculate Future Value
Project a lump sum and monthly deposits with the Future Value calculator.
Read guide →How Much Should You Invest Every Month?
Find your monthly number, then test it on the Investment Growth calculator.
Read guide →What Is the Rule of 72?
Estimate doubling time in your head, then confirm it with the Rule of 72 calculator.
Read guide → CalculatorInvestment Growth Calculator
Project the future value of a portfolio with regular contributions and compounding returns.
Category
Retirement & Independence
Setting a target, reaching it, and deciding when work becomes optional.
How Much Money Do You Need To Retire?
Turn your spending into a savings number, then test it with the Retirement calculator.
Read guide →What Is FIRE?
Financial independence explained, then find your number with the FIRE calculator.
Read guide → CalculatorFIRE Calculator
Find your financial independence number and how many years it takes to retire early.
Category
Saving & Safety
The cash foundation that lets every other plan survive a bad month.
How Much Emergency Fund Do You Need?
Size and build your buffer, then watch it grow with the Savings Growth calculator.
Read guide →How to Reach Your Savings Goals Faster
Automate, optimise and accelerate any goal, then project it on the Savings Growth calculator.
Read guide → CalculatorSavings Growth Calculator
See how regular deposits and a chosen APY grow a savings balance over time.
CalculatorCompound Interest Calculator
The flagship tool — model growth with contributions, tax and inflation in one place.
Put It Into Practice
Explore the Calculators
Theory is only half the job. Run your own numbers with the free tools that pair with these guides.
Compound Interest Calculator
See how savings and investments grow with contributions, tax and inflation.
InvestingRule of 72 Calculator
Estimate how many years it takes your money to double from a single rate.
InvestingFuture Value Calculator
Calculate the future value of a lump sum plus recurring payments.
SavingsSavings Growth Calculator
Watch a savings account grow over time with regular deposits and an APY.
RetirementRetirement Calculator
Estimate the nest egg you could have at retirement from contributions and returns.
RetirementFIRE Calculator
Find your financial independence number and years to early retirement.