Losing resolve on New Year's resolutions?

ROCHESTER, Minn. — How many calories do you have to cut to lose weight? If you exercise more, how many more calories can you consume without gaining weight? And what is a "portion" of food, anyway?

Mayoclinic.com offers a variety of free calculators and tools to help you answer those questions and stay on track to achieve your weight loss and fitness goals for the New Year. No registration is required to use these tools:

Body Mass Index

Though some know if they are overweight simply by how they look or feel, a more objective measure — one used by doctors — is a calculation of your body fat in relation to your total weight. It's called body mass index (BMI). This calculation — your weight in pounds divided by your height in inches squared — gives a fairly good approximation of body fat for most people. This calculator does the math. BMI charts indicate when it's time to lose weight.

• Tool: BMI calculator

Calorie calculator

Managing your weight always comes down to calories in and calories burned. This calculator allows you to determine a calorie count based on your activity level.

• Tool: Calorie calculator

Mayo Clinic Healthy Weight Pyramid calculator:

This isn't the U.S. government food pyramid you've seen before. MayoClinic.com's version emphasizes lower-calorie foods that help you feel full, with fruits and vegetables at the base. This calculator estimates daily calories needed to lose weight and lists how many portions of sweets, proteins, fats, carbohydrates, vegetables and fruits you can squeeze in the calorie count.

• Mayo Clinic Healthy Weight Pyramid tool

Portion control for weight loss:

Portion size is the bugaboo that can put the calorie counts off the charts. A serving of pasta is one-half cup, not a super-sized plateful. A portion of meat or fish is about the size of a deck of cards. This slide show helps you take the guesswork out of determining a portion.

• Slide show: Portion control for weight loss

Target heart rate calculator:

It's not just what you eat, but what you do. Exercising longer and harder burns more calories. But what's "harder"? An increased heart rate is one measure of intensity. This calculator provides a target heart rate range, based on age, weight and some health conditions.

• Tool: Target heart rate calculator

Calculators and calorie counts can help launch a weight loss plan. But anyone who's tried — and failed — to lose weight, or lost pounds only to regain them, knows weight management isn't easy. MayoClinic.com offers in-depth information on weight loss strategies, motivation and goal setting as well as recipes for long-term weight management success.