Learn the laws of probability with simple formulas, clear explanations, solved examples, practice questions, and an interactive calculator. Perfect for IGCSE, GCSE, IB, AP, and high school math students.

Learn the Birthday Problem with simple explanations, formulas, solved examples, practice questions, and an interactive calculator. Understand why 23 people are enough for a greater than 50% chance of a

Learn roll two dice probability with sample space, sums, outcomes, solved examples, practice questions, and an interactive calculator. Perfect for IGCSE, GCSE, IB, AP, and high school math students.

Learn Bayes’ Theorem with simple explanations, formulas, solved examples, practice questions, and a Bayes’ Theorem calculator. Perfect for IGCSE, GCSE, IB, AP, and high school students.

Use this free reverse mortgage calculator to estimate HECM loan amounts, monthly payments, fees, and remaining equity for 2026. No personal information required — 100% private.

Use this free commission calculator to estimate sales commission, real estate agent fees with broker splits, tiered commissions, and after-tax net earnings for 2026.

Use this free eBay shipping calculator to estimate USPS, UPS & FedEx shipping costs, eBay 2026 final value fees, dimensional weight, and net seller profit. The best way to calculate

Take the best free international IQ test with 40 pattern-recognition questions. Get official IQ test results with percentile ranking, bell curve visualization, and Wechsler classification. Instant, private, and scientifically normed.

Free photo sorter and batch resizer tool. Upload any image, instantly convert to Instagram, Facebook, TikTok, YouTube, website dimensions. Preview on phone, tablet, desktop and download all sizes.

Use our free Payroll Tax Refund Calculator for 2026 to estimate your FICA, Social Security & Medicare overpayment refund. Updated with $184,500 SS wage base.