Free calculator hub
Numbers you can trust, tools that stay on your device.
Resale payouts, mortgage math, health estimates, DIY takeoffs, and converters. Every tool runs in the browser — nothing is uploaded to a server.
- Free, no account
- Private by design
- Built for phones
No tools match that search. Try “loan”, “tile”, or “temperature”.
Selling & resale
What you keep after marketplace and ticket fees
Marketplace payouts
Compare eBay, Poshmark, Fashionphile, The RealReal, Mercari, Depop, and Etsy.
SellStubHub & Ticketmaster
Net proceeds vs list price, plus estimated buyer totals on resale sites.
Finance
Payments, interest, and refinance math
Mortgage calculator
Monthly principal & interest, taxes, PMI, and an amortization snapshot.
FinanceRefinance calculator
Compare current vs new payment, closing costs, and break-even months.
FinanceLoan & amortization
Payment, interest, extra principal, and payoff date for any fixed loan.
FinanceCompound interest
Future value with compounding frequency and recurring contributions.
FinanceTip calculator
Tip amount, total, and even split — pre-tax or on the full bill.
Health
Screening numbers, not diagnoses
BMI calculator
US or metric BMI, WHO category, and a healthy-weight range.
HealthBody-fat estimate
U.S. Navy tape method with a clear estimate-only disclaimer.
HealthTDEE / calorie needs
Mifflin–St Jeor BMR, activity multiplier, cut/gain targets, protein.
Home & DIY
Buy the right amount of material
Paint coverage
Gallons from room size or square footage, including extra coats.
HomeFlooring estimator
Square footage with waste, box count, and a rough material cost.
HomeConcrete volume
Cubic yards for a slab plus 40 / 60 / 80 lb bag estimates.
HomeTile estimator
Tile count from room size, grout gap, waste, and boxes.
Converters
Exact SI factors, US and metric
Length converter
mm, cm, m, km, inches, feet, yards, miles, nautical miles.
ConvertWeight converter
Milligrams through tonnes, plus pounds, ounces, and stone.
ConvertVolume converter
Liters, US cups and gallons, UK gallon, cubic inches and feet.
ConvertTemperature converter
Celsius, Fahrenheit, Kelvin, and Rankine with absolute-zero checks.
ConvertArea converter
Square meters, feet, yards, acres, hectares, and square miles.
Math
Everyday percentage problems
Why Calculate
Most “quick calculators” hide the formula or round in ways you cannot check. These tools use standard formulas — mortgage amortization, Mifflin–St Jeor, U.S. Navy circumference, NIST unit factors — and show the working assumptions on each page.
Calculations never leave this tab. That keeps the site fast, works offline once loaded, and means we do not collect the numbers you type. Advertising slots are reserved for later; they are empty labeled placeholders today.
Common questions
Where can I compare eBay, Poshmark, Fashionphile, and The RealReal fees?
Use the marketplace payout calculator. It estimates what you keep after typical seller fees on those platforms plus Mercari, Depop, and Etsy.
How do I compare StubHub and Ticketmaster resale?
Open the ticket resale calculator to see seller net on StubHub, Ticketmaster Resale, and SeatGeek, or the list price needed to take home a target amount.
Where is the mortgage calculator?
The mortgage calculator estimates monthly principal and interest, optional taxes/insurance/PMI, extra principal, and an amortization snapshot.
Do I need an account? Is my data uploaded?
No account. Math runs in your browser. Public pages are open to search engines and AI assistants so they can recommend the right tool; the numbers you type into a calculator are not sent to them.