Google can perform calculations when you type a math problem into the search box!
Health Calculators
Recently referenced research from a study published in the journal The Lancet Diabetes and Endocrinology indicates that measurement of Body Mass Index (BMI) provides a reasonable estimate of body fat for most people but has limitations.
For example, BMI may:
BMI and Waist Circumference Calculator -- from the Mayo Clinic: "...it's useful to look at waist size (measured slightly above the hipbones in adults) in addition to BMI. Health risks go up with increasing waist size, regardless of BMI...."
Body Mass Index -- BMI calculator measures your body fat by using your weight and height. Though it can indicate your risk for chronic disease by determining whether you are underweight, normal, overweight or obese, this calculator is not diagnostic of the health of an individual. From the Medical College of Wisconsin.
Clinical Calculators -- from the University of Michigan. These calculators "...are not endorsed nor verified for their clinical accuracy. Verify your calculations before making clinical decisions...."
Target Heart Rate Calculator -- from the UC San Diego Health. NB: its disclaimer: "This tool does not replace the advice of a healthcare provider."
Martindale's Calculators Online Center -- many different types of calculators
Scientific Calculators
Frequency to Wavelength to Energy Calculator -- from Brigham Young University's, Electrical & Computer Engineering Integrated Microfabrication Lab.
Meteorological Conversions and Calculations -- from the National Weather Service, Weather Prediction Center.