Calculators that show their work.

Project the growth of savings and investments with inflation-adjusted (real) returns, fees, taxes, contribution step-ups, and a full year-by-year breakdown.

CAGR, total return, and the true money-weighted return (IRR) when you add contributions — plus the inflation-adjusted real return.

Find how much to set aside each month to hit a target by a deadline — or how long your current pace will take.

What a lump sum and regular contributions grow to at any rate and compounding frequency — with the split between what you put in and the interest you earn.

The compound annual growth rate that links a starting and ending value over time — the single rate that makes investments of different lengths comparable.

Project dividend income with reinvestment (DRIP), rising payouts, and yield-on-cost — and see how much DRIP adds over taking cash.

Return on investment from what you put in and got back — plus annualized (compound) ROI, the only fair way to compare different holding periods

Turn a nominal rate into its true APY, compare APY across compounding frequencies, and see the real dollars earned.

Model contributions, employer match, and withdrawals to see whether your nest egg lasts through retirement.

Your financial-independence number, years to reach it, your Coast FIRE figure, and savings rate — all in today’s money.

Project your 401(k) with the real IRS contribution limits and catch-up — and see the employer match you’re leaving on the table.

Project tax-free Roth growth within the IRS contribution limits, and see exactly how much the tax-free growth beats a taxable account.

After-tax retirement outcomes for Roth vs Traditional — including investing the up-front tax saving and your break-even tax rate.

Estimate your benefit with the real PIA bend-point formula, and see how claiming from 62 to 70 changes your monthly check.

Required minimum distributions using the real IRS Uniform Lifetime Table, projected across every year with the estimated tax on each.

Find your gross margin from cost and price, or price a product to hit a target margin — with the markup, profit, and the margin-vs-markup distinction made clear.

Work out the markup on a product, or set a price from a target markup — and see why a markup is always a bigger number than the margin it produces.

Calculate gross profit margin from revenue and cost, see the dollar profit per unit, and price to a target margin — the number that protects your bottom line.

Return on ad spend from revenue and ad cost — plus the full funnel (CPM, CPC, CTR, conversion rate, CPA, ROI) so you see what is really driving the number.

Cost per thousand impressions from spend and impressions — with CPC, CTR, conversion rate, CPA, ROAS, and ROI for the same campaign in one view.

Your conversion rate from conversions and clicks — with cost per conversion, ROAS, and ROI so you know what each conversion costs and earns.

Click-through rate from clicks and impressions — alongside the rest of the funnel so you can tell whether a high CTR is actually converting.

Price elasticity of demand by the midpoint (arc) or point method, with the elastic/inelastic classification and the total-revenue test worked out step by step.

Consumer surplus, producer surplus, and total gains from trade — from a market price and quantity, or by solving linear demand and supply curves for equilibrium.

Solve the deflator identity for nominal GDP, real GDP, or the deflator itself — and turn two deflators into the economy-wide inflation rate between them.

The Keynesian spending multiplier from MPC — spending, tax, and balanced-budget multipliers plus the round-by-round geometric series showing where the total GDP change comes from.

The money multiplier and the maximum money a deposit can support under fractional-reserve banking, with a round-by-round lending table and a fuller model adding currency drain and excess reserves.

Deadweight loss from a per-unit tax or observed price gap — the Harberger triangle, tax revenue, trades lost, and an optional elasticity-based split of who bears the burden.