Calculators
Everyday math with the formula shown and the working visible — percentages, loans, health, dates and pay. Your numbers are processed entirely in your browser; financial and health inputs never touch a server.
- Percentage Calculator To find X% of a number, multiply the number by X ÷ 100
- Percentage Change Calculator Percentage change = (new − old) ÷ old × 100
- EMI Calculator EMI = P × r × (1+r)ⁿ ÷ ((1+r)ⁿ − 1), where r is the monthly rate and n the number of months.
- BMI Calculator BMI = weight (kg) ÷ height (m)²
- Age Calculator Your exact age is the calendar difference between today and your date of birth
- Tip Calculator Tip = bill × tip% ÷ 100
- Discount Calculator Final price = original × (1 − discount% ÷ 100)
- Compound Interest Calculator Future value = P × (1 + r/n)^(n×t)
- Simple Interest Calculator Simple interest = principal × rate × time ÷ 100
- Hourly to Salary Calculator Annual salary = hourly rate × hours per week × 52
- TDEE & Calorie Calculator Your TDEE is BMR × an activity factor
- Body Fat Percentage Calculator The U.S. Navy method estimates body fat from a few tape measurements
- Ideal Weight Calculator There is no single "ideal" weight
- Macro Calculator Macros come from your calorie target and a percentage split
- Pregnancy Due Date Calculator The classic estimate adds 280 days (40 weeks) to the first day of your last period
- Mortgage Calculator Your monthly payment is fixed, but early payments are mostly interest
- Auto Loan Calculator The monthly payment is based on the amount you actually finance
- Markup & Margin Calculator Markup is profit as a percentage of cost; margin is the same profit as a percentage of price
- Sales Tax Calculator Enter a rate that fits where you are
- Fuel Cost Calculator Trip fuel cost is simply the fuel your journey uses times the price per unit
- GPA Calculator Your GPA is a credit-weighted average of grade points
- Test Grade Calculator (EZ Grader) Score = correct ÷ total × 100. Enter how many were right out of the total and get the percentage, the letter grade and how many were missed.
- Unit Price Calculator (Price Per Unit) Unit price = price ÷ quantity. Enter two options and the calculator shows the cost per unit of each and which is the better buy.
- Overtime Pay Calculator Overtime pay = hourly rate × multiplier × overtime hours. Enter your rate and hours to get regular pay, overtime pay and the total.
- Square Footage Calculator Square footage = length × width. Enter the dimensions to get the area in both square feet and square metres, with a multiplier for repeated areas.
- Cost Per Square Foot Calculator Cost per square foot = total price ÷ area. Enter the price and the area to get the cost per square foot and per square metre.
- Dilution Ratio Calculator For a 1:N ratio and a target volume, concentrate = volume ÷ (1 + N) and the rest is water. Enter the ratio and how much you want to make.
- Aspect Ratio Calculator Pick an aspect ratio like 16:9 and type one dimension
- Sleep Calculator Set a wake-up time (or a bedtime) and get the times that fall at the end of a sleep cycle
- VAT / GST Calculator To add VAT, multiply the net price by (1 + rate); to remove it, divide the gross price by (1 + rate). At 20%, £50 net becomes £60 gross, and £60 gross is £50 net.
- Final Grade Calculator The score you need on the final = (target − current × (1 − final weight)) ÷ final weight
- Protein Intake Calculator Daily protein is set per kilogram of body weight: roughly 0.8 g/kg for general health, 1.2–1.6 g/kg if active, and 1.6–2.2 g/kg when building muscle or dieting to preserve it.
- Ovulation Calculator Ovulation typically happens about 14 days before your next period
- Pregnancy Week Calculator Pregnancy is dated from the first day of your last period, not conception
- Electricity Cost Calculator Running cost = power (kW) × hours × price per kWh. A 1500 W heater used 5 hours a day at $0.20/kWh costs 1.5 × 5 × 0.20 = $1.50 a day.
- Conception Date Calculator Conception happens around ovulation
- Days Until Date Calculator The number of days until a date is simply that date minus today
- Blood Sugar Converter (mg/dL ↔ mmol/L) Blood glucose in mg/dL ÷ 18.0182 gives mmol/L; mmol/L × 18.0182 gives mg/dL
- HbA1c Converter (%, IFCC & eAG) HbA1c in NGSP % and IFCC mmol/mol are linked by IFCC = 10.929 × (% − 2.15); estimated average glucose is eAG = 28.7 × % − 46.7 mg/dL.
- Cholesterol Converter (mg/dL ↔ mmol/L) Cholesterol in mg/dL ÷ 38.67 gives mmol/L; triglycerides use ÷ 88.57
- Creatinine Converter (mg/dL ↔ µmol/L) Serum creatinine in mg/dL × 88.42 gives µmol/L; µmol/L ÷ 88.42 gives mg/dL
- IV Drip Rate Calculator (gtt/min) Drip rate (gtt/min) = volume (mL) × drop factor (gtt/mL) ÷ time (minutes)
What you can work out here
These calculators cover the everyday math most people reach for: money — percentages, tips and discounts, loan and mortgage payments (with a full amortization schedule), and simple or compound interest; health — BMI against the WHO ranges, calorie and macro needs, and body measurements; time — your exact age, date differences and deadlines; and work and study — hourly-to-salary conversions and GPA. Each one applies the recognised formula and prints the arithmetic beneath the answer, so you can follow exactly how the result was reached rather than trust a black box.
Every calculation happens in your browser, which matters most for the sensitive numbers — a salary, a loan balance, a due date, a body measurement. Those values are never sent anywhere, so there's nothing to leak, and the pages keep working even with your connection switched off. For deeper or more specialised math, see the Mathematics, Finance and Statistics categories.
Frequently asked questions
Are these calculators accurate?
Yes — each uses the standard published formula (EMI amortization, WHO BMI ranges, compound interest), states it on the page, and shows the arithmetic under every result so you can verify it.
Is my financial or health data uploaded anywhere?
No. Every calculator runs as JavaScript in your browser. Loan amounts, body measurements and birthdates never leave your device — the pages even work offline.
Why use these instead of asking an AI chatbot?
Deterministic math: a calculator applies the exact formula every time and shows its working. Language models can make arithmetic slips, and typing your salary or health details into a chatbot shares them with a server — these tools don’t.