Calculator Categories
Nine shelves, one hundred tools. Each category page explains what its calculators are for, which one to pick when two overlap, and answers the questions people ask most about that subject.
The split is by the question you are asking rather than by the mathematics involved. Profit margin and BMI are the same arithmetic — a ratio expressed as a percentage — but nobody looking for one wants the other. So finance holds money questions, health holds body questions, construction holds "how much do I need to buy" questions, and so on.
Finance & Personal Money
20 calculatorsWork out what your money does over time: interest, savings, debt payoff, retirement targets and the household budget behind all of it.
- Compound Interest
- ROI
- Retirement
- Debt Payoff
Mortgage & Real Estate
10 calculatorsPrice a home loan properly — payment, escrow, affordability, equity, closing costs and whether renting still beats buying where you live.
- Mortgage
- Mortgage Affordability
- Home Loan
- Rent vs Buy
Business
10 calculatorsMargin, markup, break-even, growth and unit economics — the numbers that decide whether a business is actually working.
- Profit Margin
- Markup
- Break-Even
- Business ROI
Ecommerce
10 calculatorsFee stacks, shipping weights, pricing back-solves and true profit per order for Shopify, Amazon FBA and any store you run.
- Ecommerce Profit
- Amazon FBA Profit
- Discount
- Shopify Profit
Marketing & SEO
10 calculatorsCampaign maths in one place: CTR, CPC, CPM, ROAS, conversion rates, email engagement and the value of the traffic you rank for.
- Conversion Rate
- ROAS
- CTR
- CPC
Math & Statistics
10 calculatorsPercentages, fractions, ratios, roots, probability, standard deviation and area — with the working shown, not just the answer.
- Percentage
- Fraction
- Average
- Ratio
Health & Fitness
10 calculatorsEstimate BMI, BMR, TDEE, macros, body fat, hydration and running pace using the published formulas clinicians and coaches use.
- BMI
- TDEE
- Calorie
- BMR
Construction & Home Improvement
10 calculatorsQuantities before you buy: concrete, gravel, mulch, paint, tile, flooring, roofing, sand, square footage and running electricity costs.
- Square Footage
- Concrete
- Gravel
- Mulch
Education, Time & Everyday
10 calculatorsGPA, grades, attendance, ages, date gaps, shift durations and paid work hours — the small calculations that come up every week.
- GPA
- Final Grade
- Age
- Grade
How the categories overlap
A few tools could sit in two places, and where they landed is worth knowing. Sales tax is filed under ecommerce rather than finance, because most people reaching for it are pricing a product rather than doing personal accounts. Electricity cost sits in construction and home improvement, next to the other household tools, even though it is arithmetically a unit conversion. Conversion rate is in marketing while ecommerce conversion rate is in ecommerce: the first is the general metric, the second adds order value and revenue per visitor.
When a tool has an obvious partner in another category, the related block at the bottom of its page links across. That is how the health chain, the mortgage chain and the pricing chain hold together even though they span several shelves.