Answer-first guides
Each guide states the formula CalculatorX actually runs, a worked figure, and the limit of the estimate. Open the linked calculator to change the inputs.
Date & Time
Use the age calculator when you want completed years, leftover months and leftover days. Use the date-difference calculator when you want the span as a whole number of days. They are not two views of the same output. One borrows months and days. The other divides the date gap by 86,400,000 and floors the result at zero.
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Mathematics
A percentage on CalculatorX is part ÷ whole × 100. A discount is price × rate ÷ 100, subtracted from the price. A unit conversion applies one known factor, and only for kilometre/mile, metre/kilometre, kilogram/pound, and Celsius/Fahrenheit. Using the wrong page produces a confident number for a different question.
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Health & Fitness
The BMI page divides weight in kilograms by height in metres squared. Height is entered in centimetres and divided by 100. Below 18.5 is labelled Underweight, 18.5 up to 25 is Normal, 25 up to 30 is Overweight, and 30 or above is Obese. Those words are screening bands, not a diagnosis.
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Health & Fitness
The pregnancy-weeks page counts days from the first day of the last menstrual period to a reference date, then divides by 7 and shows one decimal place. It does not calculate a due date, a trimester, or a conception day. It is not medical advice.
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Loans
Both loan pages use EMI = P × r × (1 + r)^n ÷ ((1 + r)^n − 1). The EMI page takes n in months. The home-loan page takes years and sets n to years × 12. A ₹1,00,000 loan at 9% for 12 months is an EMI of ₹8,745.15. A ₹30,00,000 loan at 8.5% for 20 years is an EMI of ₹26,034.70.
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Investment
A SIP adds money every month. Compound interest grows one lump sum. Simple interest pays P × R × T ÷ 100 and does not add interest back onto the principal. A ₹5,000 monthly SIP at 12% for 10 years becomes ₹11,61,695.38 on the SIP page. ₹10,000 at 7% compounded yearly for 5 years becomes ₹14,025.52. ₹50,000 at 8% simple interest for 3 years earns ₹12,000.
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Tax
The GST page adds tax to a base: tax = base × rate ÷ 100, and total = base + tax. ₹5,000 at 18% is ₹900 of GST and a ₹5,900 total. The salary page estimates net pay as gross − (gross × tax rate ÷ 100) − other deductions in rupees. It does not use income-tax slabs.
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Health & Fitness
Daily water on this page starts at body weight in kilograms times 0.033 litres. Light activity keeps that base. Moderate multiplies by 1.2. High multiplies by 1.4. A 70 kg person at the base is about 2.31 litres. The same person at Moderate is about 2.77 litres. This is not a medical target.
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