Decision Tools

Calculate percentages: what is X% of Y, X is what % of Y, and % change.

Calculate exact age in years, months, days, hours, and minutes.

Calculate the difference between two dates in years, months, weeks, days, hours, minutes, and seconds.

Calculate mean, median, sum, min, max, range, and standard deviation for any list of numbers.

Calculate the sale price and savings from any percent-off discount.

Calculate tips and split a restaurant bill. Includes 15/18/20% side-by-side comparison.

Calculate hours worked between two times, subtract an unpaid break, and optionally estimate pay.

Estimate silent reading time and speaking-aloud time from pasted text with adjustable reading and speaking WPM sliders.

Simplify ratios, scale them up or down, and convert to decimals and percentages.

Add, subtract, multiply, and divide fractions. Shows simplified result, mixed number, and decimal.

Calculate exactly what X% of Y equals, with quick-math anchors for 1%, 10%, 25%, and 50%.

Calculate the percent change from one value to another — increase or decrease — with exact delta and ratio.

Calculate how old you will be — or were — on any target date. Works for past and future dates.

The exact date a side-hustle can sustainably replace a primary salary, factoring self-employment tax and benefits loss.

Should you hire a human at $X/hr or pay $Y/mo for a SaaS/automation stack? Efficiency bar comparison.

Is your time worth more than the professional quote? Balance-scale verdict with DIY cost vs outsourcing.

When does a $2k cloud bill justify an $8k rack? Crossover math with depreciation, electricity, and uptime risk.

The absolute minimum hourly rate to match a corporate salary after self-employment tax, benefits, and non-billable time.

What this $10k would be worth in 10, 20, or 30 years if invested instead. Compound-growth opportunity-cost filter.

Quantify the compounding hours to fix a shortcut as the codebase grows on top of it. Maintenance heatmap.

Estimate whether the next hire raises or lowers revenue per employee after management time and ramp-up.

Most calories per dollar spent — survival math for when the food budget is hard-capped.

What DoorDash or Uber actually pays after IRS mileage depreciation — real hourly vs the minimum wage floor.

When you can't pay everything, which bill first? Weighted ranking by service-cutoff risk and late-fee pain.

Turn abstinence from a habit into dollars saved toward something you actually need.

Weighed social ROI — does the connection payoff beat the transit, cost, and energy tax of leaving the house?

Compute the true APR of a payday loan, pawn redemption, or cash advance — with a predatory heatmap from fair to extortionate.

Estimate when extra work hours stop being worth the fatigue cost from lost sleep.

Rank food by kilocalories per dollar and convert grocery spend into days of biological uptime at a 2,000 kcal baseline.

Prioritize essential bills first when there is not enough cash to pay everything.

Compare gig earnings with the estimated vehicle wear created by the miles driven.

Compare the benefit of a social plan against the time, energy, and money it costs.

Boots-theory math: cheap-vs-quality cost per day over a 5-year horizon, with an injustice-gap total.

Real hourly wage after transit time (uncompensated labor) and transit cost eat into shift earnings.

Should you sell an asset to avoid a late fee? Replacement penalty vs fee avoided — equity loss meter.

What percent of your labor pays for the sanity premium of living alone vs with a roommate? Peace-vs-capital slider.

Calculate how many units you must sell to cover fixed costs — break-even quantity and revenue.

Convert between cost, price, markup, and margin. Shows profit, markup %, and margin % from any two inputs.

Calculate your monthly mortgage payment with taxes, insurance, HOA, and PMI. See total interest and what each 1% rate change really costs.

See how extra payments change your payoff date and total interest. Monthly, annual, or one-time — all scenarios side by side.

Calculate markup percent, selling price, and gross profit from cost. Shows how a price change affects the markup.

Calculate gross margin, profit, and the price required to hit a target margin. Shows equivalent markup alongside.

See when you'll hit your savings target and how extra contributions or growth change the timeline.

Estimate the melt value of gold jewelry or bullion by weight, karat, and the current spot price per gram.

Convert the mass of a gold piece between karats while keeping the pure-gold content constant. 24K to 22K, 22K to 18K, 14K to 10K — all covered.

Stack a sale, coupon, extra discount, senior or loyalty percent, tax, and cashback rebate in one calculation. See the effective discount and net cost.

See how many days are left in the current year, how many have elapsed, and the percent of the year complete. Leap-year aware.