Quick, clean calculators
for everyday questions
Free tools that load instantly and give you the answer the moment you type. No signup, no clutter, works on any device.
Everyday
the essentialsAge Calculator
Your exact age in years, months, days — plus total days lived and next birthday.
OpenPercentage Calculator
What is X% of Y, percentage change, and “X is what % of Y” — with the formula shown.
OpenUnit Converter
Length, weight, temperature, volume and speed. Plus fast pages for cm↔in, kg↔lb and more.
OpenHealth & Dates
track yourselfCalorie Calculator
Your daily calories (TDEE) and BMR, with targets to lose, keep or gain weight.
OpenDue Date Calculator
Estimate your pregnancy due date, how many weeks along you are and your trimester.
OpenBMI Calculator
Body Mass Index with your category, a visual scale and your healthy weight range.
OpenDays Between Dates
Count the days, weeks and months between two dates — with a working-days option.
OpenMoney
plan your financesCompound Interest
See how savings and investments grow over time, with a chart and yearly breakdown.
Open High valueSalary Calculator
Turn gross pay into take-home by month, week, day and hour using your own tax rate.
Open High valueLoan & Mortgage
Monthly payment, total interest and a full amortization schedule for any loan.
Open High valueFIRE Calculator
Your FIRE number, savings rate and the age you could retire — with a growth chart.
OpenPopular conversions
one tap eachCM to Inches
Convert centimetres to inches with a quick-reference table.
ConvertKG to Lbs
Convert kilograms to pounds instantly.
Convert°C to °F
Celsius to Fahrenheit with the formula explained.
ConvertKM to Miles
Kilometres to miles for runners and drivers.
ConvertFeet to Meters
Feet to metres for height and distance.
ConvertAll converters →
Inches↔cm, lbs↔kg, miles↔km, °F↔°C and more.
BrowseFree online calculators that just work
CalcBoxes is a growing collection of small, fast, single-purpose calculators. Each tool does one thing well and shows the result the instant you type — no “calculate” button to hunt for, no account to create, and no data leaving your device. Every calculation runs entirely in your browser.
We built CalcBoxes because most calculator sites are slow and buried under pop-ups. Ours load in well under two seconds, work beautifully on a phone, and explain the maths behind every answer so you can check the result yourself. Whether you need your exact age, a quick percentage, your BMI, a loan payment, or a cm-to-inches conversion, the answer is one tap away.
Why people use CalcBoxes
- Instant. Results update live as you type — no waiting, no reloads.
- Private. Everything is calculated locally in your browser. We don’t store what you enter.
- Clear. Each tool shows the formula and worked examples, so you understand the answer.
- Free. No signups, no paywalls, no limits. Ads keep the lights on; the tools stay free.