Adjusted Body Weight Calculator

This free adjusted body weight calculator finds your adjusted body weight (AdjBW) and your ideal body weight (IBW) in kg and lb. It uses the Devine formula for ideal body weight, then applies the standard 0.4 correction factor to reach a dosing weight.

Doctors and pharmacists use adjusted body weight when a person’s actual weight is well above their ideal weight. Many medicine doses are safer when they are based on a weight between the two values, rather than on actual weight alone. If you also want a general weight check, start with the BMI Calculator and then return here for a dosing weight.

You only need three facts: your sex, your height and your actual body weight. Enter them below and the tool shows both results at once, in kilograms and in pounds. No sign up is needed, and the calculation happens on this page in seconds.

What Is Adjusted Body Weight and Why Is It Used?

Adjusted body weight is a weight value used for medicine dosing. It sits between ideal body weight and actual body weight. It is made by taking ideal body weight and adding 40 percent of the gap between actual weight and ideal body weight.

It is used when a person’s actual weight is well above their ideal weight. In that case, dosing a medicine on actual weight alone could give too much of the drug. Dosing on ideal weight alone could give too little. Adjusted body weight offers a middle value that many dosing guides accept.

A common example is a person with obesity who needs a weight based medicine. Their fat tissue does not take up some drugs in the same way as lean tissue does. So a dose based on total body weight can overshoot the amount the body can handle. Adjusted body weight helps to keep the dose closer to a safe range.

How to Use This Adjusted Body Weight Calculator

Using this adjusted body weight calculator is simple. Follow these steps and you will have both results in a few seconds.

1. Choose your sex, male or female.
2. Enter your height in feet and inches.
3. Enter your actual body weight and choose kg or lb.
4. Click the Calculate Adjusted Body Weight button.
5. Read your ideal body weight and your adjusted body weight, each shown in kg and lb.

For the best result, use your current weight and a height measured without shoes. If you weigh yourself at home, weigh in the morning before eating, in light clothes, and use the same scale each time. For daily energy needs, pair this result with the TDEE Calculator, which estimates how many calories you burn each day.

Adjusted Body Weight Formula

The adjusted body weight calculator uses two steps. First it finds ideal body weight with the Devine formula. Then it adjusts that value toward your actual weight.

Devine ideal body weight for men: IBW = 50 kg + 2.3 kg for each inch over 5 feet. Devine ideal body weight for women: IBW = 45.5 kg + 2.3 kg for each inch over 5 feet. The base value is the ideal weight for a person who is 5 feet tall. Each extra inch adds 2.3 kg.

Adjusted body weight: AdjBW = IBW + 0.4 x (actual weight – IBW). The 0.4 factor means that only 40 percent of the extra weight above ideal weight is counted. The other 60 percent is left out, because it is treated as excess tissue that should not carry a full dose.

This 0.4 factor is the standard value used in most dosing guides. Some guides use a different factor for a specific drug, so a doctor or pharmacist may use another value in a special case. This calculator uses 0.4, which is the widely accepted default.

Worked Example

Here is a worked example with the same numbers you can try in the tool above. Take a man who is 5 feet 10 inches tall and whose actual weight is 100 kg.

1. Height in inches: 5 feet 10 inches is 70 inches.
2. Inches over 5 feet: 70 – 60 = 10 inches.
3. Ideal body weight: IBW = 50 + (2.3 x 10) = 50 + 23 = 73 kg.
4. Adjusted body weight: AdjBW = 73 + 0.4 x (100 – 73) = 73 + 0.4 x 27 = 73 + 10.8 = 83.8 kg.
5. In pounds: IBW is 160.9 lb and AdjBW is 184.7 lb.

So for this man, the dosing weight is 83.8 kg. That is 16.2 kg below his actual weight of 100 kg, and 10.8 kg above his ideal weight of 73 kg. It is the middle value that a dosing guide would most likely use.

When to Use Adjusted Body Weight vs Actual and Ideal Weight

Use adjusted body weight when actual weight is well above ideal weight and the drug dose is weight based. This is the usual case for people with obesity. It is also the case when a dosing guide for a specific drug says to use adjusted body weight. In those cases, AdjBW is the safest middle ground.

Use actual body weight when a person is near their ideal weight, or when the drug dose is meant to follow total body weight. Many drugs are dosed on actual weight for people who are not overweight. A dosing guide will say so when that is the case. Do not guess which weight a drug needs.

Use ideal body weight when a person is underweight, or when the drug is one that should not be dosed on excess weight at all. Ideal body weight is also used for some lung and kidney measures. Again, the drug guide and the prescribing clinician decide which weight applies.

The key point is simple. Actual weight, ideal weight and adjusted body weight are three different tools. Each one fits a different case. If you are unsure which one applies to a medicine, ask a doctor or pharmacist before you take it.

Limitations of Adjusted Body Weight

Adjusted body weight is an estimate, not an exact measure of how a drug will act in your body. The Devine formula was built for adults, and it works best for people who are at least 5 feet tall. It does not suit children, and it needs care in pregnancy, in older age and in people with very low muscle mass.

The formula also does not measure body fat, muscle, water or organ function. Two people with the same height, sex and weight can have different body shapes and different drug needs. Kidney and liver function also change how a drug is handled, and no weight formula can capture that.

For those reasons, always treat the result as a starting point for a clinician, not as a dose to take on your own. A doctor or pharmacist should confirm the dose, the drug and the weight to use. For a food based weight plan, the Calorie Calculator can help you plan daily intake around your goals.

FAQs About the Adjusted Body Weight Calculator

What is adjusted body weight?

Adjusted body weight is a dosing weight that sits between ideal body weight and actual body weight. It is ideal body weight plus 40 percent of the weight above ideal body weight, and it is used when actual weight is well above ideal weight.

How is adjusted body weight calculated?

First, ideal body weight is found with the Devine formula, using sex and height. Then adjusted body weight is found with the formula AdjBW = IBW + 0.4 x (actual weight – IBW). This calculator does both steps for you and shows the results in kg and lb.

Is adjusted body weight the same as ideal body weight?

No. Ideal body weight depends only on sex and height. Adjusted body weight also uses actual weight, so it is higher than ideal body weight whenever actual weight is above ideal weight. When actual weight equals ideal weight, the two values are the same.

Who should use an adjusted body weight calculator?

It is most useful for adults whose actual weight is well above their ideal weight, and for health workers who need a dosing weight for such a person. Students and carers can also use it to learn how dosing weights are worked out.

Can I use adjusted body weight for any medicine dose?

No. Some drugs use actual weight, some use ideal weight, and some use adjusted body weight. The correct weight depends on the drug and on the person. Always follow the dosing guide for that drug and check with a doctor or pharmacist.