Free Online Calculators

Free online calculators for finance, math, marketing, and statistics. Every calculator runs instantly in your browser — no registration, no downloads, no subscription.

Whether you need to calculate GST on an invoice, find the monthly EMI on a loan, work out a percentage increase, or compute your AdSense earnings from traffic data — this calculator suite covers the most common real-world calculation needs. All calculations run client-side: your financial data never leaves your device.

Percentage CalculatorCalculate % of a number, percentage change, or reverse-calculate the base.Age CalculatorFind your exact age in years, months, and days from your date of birth.GST CalculatorAdd or remove GST. Supports all Indian GST slabs with CGST/SGST split.Loan / EMI CalculatorCalculate monthly EMI, total interest, and total repayment for any loan.Discount CalculatorFind sale price after any % discount and reverse-calculate the original price.AdSense CalculatorEstimate monthly Google AdSense earnings from page views, CTR, and CPC.Average CalculatorCalculate mean, median, mode, and range of any set of numbers.Confidence Interval CalculatorCompute 95% or 99% confidence intervals from sample mean, SD, and n.CPM CalculatorSolve for CPM, total ad spend, or total impressions from any two values.Margin CalculatorCalculate gross profit margin, markup %, and selling price from cost.PayPal Fee CalculatorFind out how much PayPal takes and how much to invoice to receive a target amount.Probability CalculatorCalculate probability of single events, AND, OR, and complementary events.Sales Tax CalculatorAdd or remove sales tax from any price at any rate.

Frequently Asked Questions

Are these calculators completely free?

Yes, all calculators on GoodToolIt are 100% free with no sign-up, no subscription, and no hidden costs.

Is my financial data safe?

All calculations run inside your browser. No data is sent to any server.

Which calculator should I use for loan repayments?

Use the Loan Calculator (EMI Calculator) — enter the principal, annual interest rate, and tenure to get your monthly EMI, total interest, and total repayment.

Can I calculate GST in both add and remove mode?

Yes. The GST Calculator works in both directions: add GST to a base price, or remove GST from a GST-inclusive price.