Calorie Calculator

How the Calorie Calculator Works

The calculator uses the Estimated Energy Requirement (EER) equations from the Institute of Medicine’s 2005 Dietary Reference Intakes. An EER is the average daily energy intake predicted to keep a healthy adult’s weight stable, given their age, sex, height, weight and physical activity level.

It’s a maintenance estimate. It describes how many calories match what the body uses, not a target for gaining or losing weight.

The EER Equations

For adults 19 and older with a BMI from 18.5 to 25 (weight in kg, height in meters):

Men: EER = 661.8 − 9.53 × age + PA × (15.91 × weight + 539.6 × height)

Women: EER = 354.1 − 6.91 × age + PA × (9.36 × weight + 726 × height)

PA is the physical activity coefficient:

Activity level	Men	Women
Sedentary	1.00	1.00
Low active	1.11	1.12
Active	1.25	1.27
Very active	1.48	1.45

For adults with a BMI over 25 the Institute of Medicine published a separate set of equations:

Men: EER = 1,085.6 − 10.08 × age + PA × (13.7 × weight + 416 × height), PA 1.00 / 1.12 / 1.29 / 1.59

Women: EER = 447.6 − 7.95 × age + PA × (11.4 × weight + 619 × height), PA 1.00 / 1.16 / 1.27 / 1.44

The calculator works out your BMI from the height and weight you enter and applies the matching set.

Worked Example

A 30-year-old man, 5 ft 9 in (1.7526 m) and 160 lb (72.57 kg). His BMI is 23.6, so the BMI 18.5–25 equation applies.

• Age term: 661.8 − 9.53 × 30 = 375.9
• Body-size term: 15.91 × 72.57 + 539.6 × 1.7526 = 1,154.7 + 945.7 = 2,100.4
• Sedentary (PA 1.00): 375.9 + 2,100.4 = 2,476 calories/day
• Low active (PA 1.11): 375.9 + 1.11 × 2,100.4 = 2,707 calories/day
• Active (PA 1.25): 375.9 + 1.25 × 2,100.4 = 3,001 calories/day
• Very active (PA 1.48): 375.9 + 1.48 × 2,100.4 = 3,484 calories/day

The jump from sedentary to very active is more than 1,000 calories a day, which shows how much activity level matters.

Using the Result Well

It’s an average for people like you

The equations predict what’s typical for a healthy adult with your measurements. Individual needs differ, so the number is a starting estimate. Changes in body weight over a few weeks are a more direct sign of whether intake matches use.

Be honest about activity

Activity level has the biggest effect on the result. Choosing a higher level than your usual week overstates the estimate. The calculator shows all four levels so you can compare.

Weight change isn’t covered

These are maintenance equations. Planning to gain or lose weight involves more than subtracting a fixed number of calories, because the body’s energy use changes as weight changes. A doctor or registered dietitian can help with weight goals, and the NIH Body Weight Planner models changes over time.

Not for everyone

The equations don’t apply to children, or during pregnancy or breastfeeding, and may not fit people with medical conditions that affect metabolism. For resting energy only, use the BMR calculator; for daily fluids, see the water intake calculator.