JavaScript I wrote:

Calculate the interest on a security deposit.

Play "What's My Word?" with scoring help.

Find the date of Easter in any Gregorian year.

Determine a 13-digit ISBN from a 10-digit ISBN

See how a book title changes with one letter removed

Learn your target heart rate for exercising

Metric Conversion:

Temperature conversion:

Fahrenheit to Celsius

Celsius to Fahrenheit

Weight conversion:

Pounds to kilograms

Kilograms to pounds

Calculate your target heart rate

Enter your information below to generate a table of target heart rates.

The table will show heart rates for 50 to 85 percent of your heart rate reserve. Your heart rate reserve is the difference between your maximum heart rate and your resting heart rate. Your maximum heart rate is calculated by subtracting your age from 220. Your target rate is calculated by finding the target percentage of your heart rate reserve and adding it to your resting heart rate.

You should achieve a minimum of 50 percent of your reserve and not exceed 85 percent.

Enter your age (in number form):

Enter your resting heart rate (your pulse for one minute—see bottom of page) (in number form):

Your result will appear here.

Need to find your resting heart rate?

Find your pulse, use this timer to time it for 15 seconds, and multiply by four.

Number of seconds*:
Countdown: 00:15:00

*You can change the number of seconds and hit Reset for a shorter or longer time.

Okay, need help multiplying?
Enter your pulse count: Enter the number of seconds you counted: