How do you calculate ideal and adjusted body weight for a client?
In short: Ideal body weight (IBW) is a height- and sex-based reference weight used in some clinical calculations, commonly estimated using formulas such as Devine or Robinson. Adjusted body weight (AdjBW) incorporates a proportion of the difference between actual and reference weight and is used in some clinical protocols for people with obesity. There is no single universally accepted IBW formula or AdjBW correction factor, so use the method specified by the guideline or protocol you are following. These are calculation tools, not target weights for clients.
1 min 16 s videoCaptions onUpdated 4 October 2026
What each weight is for
These are working numbers for calculations, not judgements about how a client should look. Use the weight that fits the sum you're doing.
Although traditionally called ideal body weight, IBW is better understood as a reference weight for particular calculations, not an ideal weight for the individual.
| Weight | What it is | Where practitioners use it |
|---|---|---|
| Actual weight | The client's current measured weight | Many energy and nutrition calculations, depending on the equation or guideline |
| Ideal body weight | A reference weight estimated from height, sometimes incorporating sex | Some clinical calculations and as a component of certain adjusted-weight formulas |
| Adjusted body weight | A calculated weight between a reference weight and actual weight | Some clinical protocols for people with obesity when specified by the relevant guideline |
The formulas
The IBW formulas were written in inches, with 60 inches (152.4 cm) as the baseline. Convert height first, then add a fixed weight for every inch above 5 feet.
Inches over 5 ft = (height in cm − 152.4) ÷ 2.54
Devine men: IBW = 50 + (2.3 × inches over 5 ft)
women: IBW = 45.5 + (2.3 × inches over 5 ft)
Robinson men: IBW = 52 + (1.9 × inches over 5 ft)
women: IBW = 49 + (1.7 × inches over 5 ft)All answers are in kilograms. Devine published his formula in 1974 for drug dosing, without saying where the numbers came from.
One commonly used form of the adjusted body weight formula is: AdjBW = IBW + correction factor × (actual weight − IBW)
The correction factor is not standardised. Values such as 0.25 and 0.4 appear in different clinical protocols, and the appropriate method depends on what the adjusted weight is being used for.
Follow the formula specified by the relevant guideline or service rather than assuming one correction factor applies universally.
A worked example
Your client is a 45-year-old woman, 165 cm tall, weighing 110 kg (BMI 40.4). You want a protein target of 1.2 g/kg. The adjusted weight below uses a correction factor of 0.25 as an example calculation, not as the universal adjusted-weight formula.
Inches over 5 ft = (165 − 152.4) ÷ 2.54 = 4.96 Devine IBW = 45.5 + (2.3 × 4.96) = 56.9 kg Robinson IBW = 49 + (1.7 × 4.96) = 57.4 kg AdjBW (example using 0.25) = 57.4 + 0.25 × (110 − 57.4) = 70.6 kg Protein on actual weight: 110 × 1.2 = 132 g Protein on adjusted weight: 70.6 × 1.2 = 85 g Protein on ideal weight: 57.4 × 1.2 = 69 g
The three methods produce very different protein targets: 69 g/day using IBW, approximately 85 g/day using the example AdjBW calculation, and 132 g/day using actual weight.
This demonstrates why the choice of body weight can substantially affect a per-kilogram prescription in a client with obesity.
It does not mean that the adjusted-weight result is automatically the correct target; the appropriate method should be determined by the population, clinical context and guideline being followed.
For how to set the per-kilogram figure, see How to work out a client's protein needs.
Where these numbers mislead
- Energy equations. The Mifflin-St Jeor equation was developed using actual body weight and included participants with obesity. Substituting IBW or AdjBW changes the equation from the method that was validated.
- Muscular clients. A client with high muscle mass may sit substantially above an IBW estimate despite having relatively low body fat. In this situation, an IBW- or obesity-based adjusted-weight calculation may be inappropriate. Use a method suited to the client's body composition and the purpose of the calculation.
- Very short or tall clients. Height-based IBW equations may become less appropriate at the extremes of height. Use a population- and purpose-specific method where available rather than automatically applying the formula.
- Pregnancy, children, amputations and significant fluid shifts. Standard adult IBW and AdjBW equations may be inappropriate in these circumstances. Use the relevant specialist guidance and account for factors such as altered body composition or fluid status.
- Goal setting. Despite the name, 'ideal body weight' should not automatically be interpreted as a client's ideal or target weight. In the worked example, the Robinson equation produces an IBW of approximately 57 kg, but that does not mean 57 kg is an appropriate weight-loss goal for this client. Weight-management goals should be individualised separately from any reference weight used for a clinical calculation.
If discussing the calculation with a client, make clear that IBW is a technical reference value rather than a judgement about what they should weigh.
How to do it in Foodzilla
Foodzilla doesn't calculate adjusted body weight. If the Weight Goal field is left blank when adding a client, Foodzilla uses the Robinson IBW calculation to populate the field. Because IBW is a reference value rather than an individualised weight-loss goal, review this figure and replace it with an appropriate goal where necessary. Adjusted body weight, where required by the guideline or protocol you are following, needs to be calculated separately.
- 1Go to Clients, then Add Client. When the client's goal is to lose or gain weight, a Weight Goal field appears beside Goal Timeframe. If you leave Weight Goal blank, Foodzilla populates this field using the Robinson IBW calculation. Review this value rather than assuming it represents an appropriate goal weight for the client.
- 2For an existing client, open their dashboard, choose Health & Diet Goals and stay on the Health tab. Press the pencil on the Weight Goal card and enter the individualised goal weight you have agreed for the client rather than automatically using the IBW value.
- 3If the profile is complete, Foodzilla recalculates Daily Energy In from the new goal weight and Goal Timeframe and rescales the macros. Its BMR always uses the current weight in the profile.
- 4Go to the Nutrition tab and edit Daily Protein In using the protein target you have determined for the client. If your chosen guideline or protocol specifies adjusted body weight, calculate this separately and enter the resulting protein target here. Daily Energy In changes by 4 kcal for every gram of protein you add or remove, so check the overall energy and macronutrient targets afterwards.
- 5Back on the Health tab, read How these targets are calculated to see the client's maintenance energy, daily target and pace towards the goal weight.
Good to know
- Write down the methodRecord which IBW formula and, where relevant, which adjustment factor you used. Different methods can produce different results, so documenting the calculation makes it easier to interpret and reproduce later.
- Reassess when relevantIf a calculation uses actual or adjusted body weight, the result may change as body weight changes. Reassess it periodically and when there has been a meaningful change in weight, body composition, clinical status or treatment.