Learn the math behind smart decisions
Short guides plus hand-picked lessons from respected educators — each linked to a calculator so you can apply it immediately.
Quick guides
The 5-number money checkup
Your savings rate, emergency-fund months, debt-to-income, net worth trend and retirement gap. If you know these five numbers, you know where you stand. Start with the savings goal and debt payoff tools.
Rule of 72, explained
Divide 72 by an annual growth rate to estimate the years it takes to double: 72 ÷ 8% ≈ 9 years. The same trick works for inflation — at 3%, prices double in about 24 years.
Why APR beats the headline rate
APR folds in many fees and gives a truer cost of borrowing. Two loans with the same rate can have very different APRs.
AI costs for small businesses
Token pricing scales with usage. Measure average prompt and reply sizes, cache what repeats and route easy tasks to smaller models. Our AI cost estimator models it.
Video lessons
Videos are embedded from YouTube using privacy-enhanced mode and remain the property of their creators.
Compound interest
Try the matching calculator →How mortgage rates work
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Try the matching calculator →Emergency funds
Try the matching calculator →Generative AI basics
Try the matching calculator →How neural networks learn
Try the matching calculator →Turn your numbers into a plan.
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