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i don't know how to apply Switch statement to bmi calculator

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Posted on by ojobabs

Hello, I recently started with power apps and one of the very first app I am building is a Body mass index(BMI) calculator. I was able to set it to automatically convert from Kg to pounds and cm to feet. The problem I am facing now is outputting the result using IF or Switch statement to show the BMI categories

BMI Categories:
Underweight = <18.5
Normal weight = 18.5–24.9
Overweight = 25–29.9
Obesity = BMI of 30 or greater

The formula I intend to use is

BMI = 703* (weight/(Height^2))

This is the logic I used

Set(VarResult,If(tx1.Text/(tx2.Text^2)*703)=<18.5,"underweight")
if(VarResult>18.5,"Normal")
if(VarResult>=24.5,"Overweight")
if(VarResult>30, "Obese")).

Please help

Categories:

Building Power Apps

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timl 36,383 Super User 2025 Season 2 on at

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Hi @ojobabs

The Switch function looks for an exact match, therefore, a simple way to do this would be to use if statements.

With this example, you could set the text property of a label to the following formula to show the BMI result.

With({res:Value(tx1.Text)/(Value(tx2.Text)^2)*703}, If(res<=18.5, "Underweight", res<=24.5, "Normal", res<=30, "Overweight", "Obese" ) )

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ojobabs 14 on at

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You fully broke down the select statement, but your answer does not solve my problem. After running your code, I keep getting "underweight" for correct values. Furthermore, I am working on improving my calculations. Thanks for assisting.

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Drrickryp Super User 2024 Season 1 on at

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Your With statement is incorrect. Also there is no need for Value() arithmetic operators automatically convert text to numbers in PowerApps.

With({res:(tx1.Text) / (tx2.Text) ^ 2 * 703}, If(res <=18.5, "Underweight", res <=24.5, "Normal", res <=30, "Overweight", "Obese" ) )

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timl 36,383 Super User 2025 Season 2 on at

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@ojobabs

The only thing that might be wrong here is the placing of the parenthesis.

With({res:(tx1.Text / (tx2.Text) ^ 2) * 703}, If(res <=18.5, "Underweight", res <=24.5, "Normal", res <=30, "Overweight", "Obese" ) )

Whilst, @Drrickryp is correct in that PowerApps will implicitly convert text to numbers, I used Value to explicitly carry out the conversion to avoid any ambiguity.

If that still doesn't work, I would set the text property of a label to the following formula to investigate whether the underlying calculation produces the expected value:

(tx1.Text / (tx2.Text) ^ 2) * 703

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ojobabs 14 on at

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Thank you all for your help, the calculation error is from my end.
Below is the correct equation
With(
{res:Value(tx1.Text)/(Value(tx2.Text)^2)*10000},
If(
res>= 30, "Obese",
res> 25 && res< 29.9, "Overweight",
res> 18.5 && res< 24.9, "Normal",
res<= 18.4, "Underweight"
)
)

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