CalcTray is a free library of online calculators for finance, health, math, and everyday decisions. Work out a mortgage payment, loan cost, or compound interest. Check your BMI, BMR, or GPA. Solve geometry. Every calculator runs in your browser with no signup and no download, and shows the steps behind the answer so you can check the math yourself. Prefill the inputs, share a link to your result, or embed a calculator on your own site. Fast on any phone, and ready the moment you land.