Money questions, worked out rather than argued about.
Most financial advice tells you what to do. These explain the arithmetic underneath, then hand you the model that produced it so you can run your own numbers. Every figure comes from a calculator on this site, and each guide says plainly where its answer stops being reliable.
All guides
Pay off the mortgage or invest?
Prepaying a mortgage earns exactly your interest rate, guaranteed. So the break-even is one number, and at 6.5% the two paths finish $3 apart on $221,000.
Read the guide →Is leasing a car throwing money away?
You pay for depreciation either way. Three routes to the same car land within $751 of each other over three years, and the answer changes in month 37.
Read the guide →Snowball or avalanche?
Avalanche saves $728 here, and the gap scales with how far apart your rates are. But the extra $250 a month is worth five times either method.
Read the guide →How much do I need to retire?
25 times your spending fails about one time in four. A flat-return calculator says $2.00M; allow returns to vary and the median life ends with $725k.
Read the guide →How much house can I afford?
A lender approves you on gross income. You pay from take-home. The 28% rule is really 39% to 42% of the money that actually arrives.
Read the guide →Computed, not asserted
Anyone can tell you extra mortgage payments save money. These guides show you how much, using the same models the calculators run, and check the figures against a second method before publishing. Where the answer depends on an assumption, the guide says which one and shows what happens when it changes.