Some fun with JavaScript calculators.

Monthly Payment Calculator

JavaScript program for computing monthly payments using the formula:
M = P * ( J / (1 - (1 + J) ^ -N))
M is the monthly payment,
P is the principle amount,
I is the interest rate in percent: 1-100%
J is monthly interest in decimal form = I / (12 x 100),
and N is number of months over which loan is amortized. For a detailed amortization schedule and the affects of extra payments, see Bankrate.com Loan Calculator

Pool Volume Calculator (US Gallons)

Round Pool (Enter the pool radius and click Compute to find the gallons)
Radius: Feet	Depth: Feet	Gallons

Rectangular Pool (Enter the pool width, length, and depth; then click Compute to find the gallons)
Width: Feet	Length: Feet	Depth: Feet	Gallons

The Popular, Mother of All Cousins Calculators

Arithmatic Drills

Lauch the Multiplication Table Drill