Site map

A single page listing every public calculator and major section. Use it to jump directly to a tool, or to see how the site is organized. Machine readable listings for search engines live at sitemap.xml (and the sitemap index). For the same list with a different entry point, see All calculators.

Howdeedo groups tools by intent: finance (loans, taxes, savings), health and fitness, math and education, everyday utilities, and date and time. Each page documents assumptions and formula version so results are reproducible and citable—whether you use the web UI or the public API.

Finance

Compound interest — How $10K becomes $30K (or $100K) depending on rate, time, and whether you keep adding to it.
Debt payoff — Months to payoff and total interest from balance, rate, and payment. Credit card planning.
Discount — Final price and savings from percentage discount. Perfect for sales and coupons.
House affordability — Total monthly housing cost: rent or mortgage, taxes, insurance, maintenance, and more. See what you'll pay and what share of income it is.
Loan — Monthly payment and total interest for a fixed-rate loan. Personal loans, auto loans—same formula lenders use.
Mortgage — Monthly payment, total interest, and what happens when you change the rate by half a point. (Spoiler: it's a lot.)
Retirement — Projected balance from starting amount, annual contribution, rate, and years.
Salary to hourly — Convert between annual salary and hourly rate. Monthly and weekly.
Sales tax — Add or remove sales tax. Pre-tax to total or total to pre-tax.
Simple interest — Interest and total from principal, rate, and time. Linear interest, no compounding.
Tax bracket — US Federal income tax for 2024. Total tax, effective rate, marginal rate by bracket.

Health & fitness

Blood alcohol content — Blood Alcohol Content estimate from drinks, weight, sex, and time. Widmark formula. ESTIMATE ONLY.
BMI — Height, weight, one number. We'll tell you what the ranges mean and what they don't.
Calorie — BMR and TDEE from weight, height, age, sex, and activity. Mifflin-St Jeor.
Child growth BMI — BMI-for-age percentile for children 0-19 years. WHO growth standards, sex-specific.
Child growth chart — WHO growth percentiles with multiple measurements. Height-for-age, weight-for-age, and more.
Child growth weight-for-length — WHO weight percentiles for infants 0-24 months. Weight-for-length, sex-specific.
Pregnancy due date — Estimated due date from LMP. Naegele rule. For planning only.
Running pace — Minutes per mile or km from distance and time. Perfect for runners and race planning.

Math & education

GPA — Letter grades and credits to cumulative GPA. Standard 4.0 scale.
P-value — Statistical significance from z-test or t-test. Hypothesis testing at α = 0.05.
Percentage — What's 18% of $47.50? Percent change? Increase, decrease? We won't judge why you need this at 11pm.
Random number generator — Generate a random integer between min and max. Cryptographically secure.
Test grade — Score and total to percentage and letter grade. Standard scale.

Everyday

Concrete slab estimator — Estimate concrete slab volume from length, width, and thickness with cubic yard and bag-style outputs.
Currency converter — Convert between major currencies. Fixed rates, quick estimates for travel and shopping.
Drywall estimator — Estimate drywall sheet count for walls and ceilings with waste adjustment and rounded purchase totals.
Fertilizer estimator — Calculate lawn fertilizer bags. Based on nitrogen content and application rate.
Flooring estimator — Calculate flooring boxes for wood, laminate, or LVP. Boxes needed with waste factor.
Fuel cost — Trip fuel cost from distance, MPG/L100km, and price. Road trip budgeting.
Gravel estimator — Estimate gravel quantity by area and depth with cubic yards, tons, and density-aware conversion.
Materials estimator — Material estimators for paint, flooring, tile, concrete, and more. Pick a calculator from the hub.
Mulch estimator — Estimate mulch or soil volume from area and depth, with cubic yards and bag count outputs.
Paint estimator — Estimate paint quantity for walls and ceilings with coats, coverage rate, and buy rounding.
Seed & sod estimator — Calculate grass seed or sod rolls. Choose seed or sod mode for lawn coverage.
Tile estimator — Calculate tile count for floors and walls. Accounts for tile size and waste.
Tip — Tip, total, and split — so the table isn't doing mental math while the server waits.
Trim estimator — Calculate baseboard and trim sticks. Linear feet to pieces needed.
Unit converter — Cups to liters, Fahrenheit to Celsius, pounds to kilograms. The stuff you Google three times a week.

Date & time

Age — Age in years, months, and days from birth date. Total days.
Date difference — Days, weeks, and months between two dates.
Time duration — Duration between start and end times. Handles day boundaries automatically.