Comping out Recent Sales to calculate ARV

[Samson Kay]

Just wanted to get everyones opinion on the following method for calculated ARV.

I have 3 recent sales all 3 BR 1- 2 bath with a garage, But the square footage is much smaller and overall lot size is also much smaller compared to the property in question.

Is it acceptable to use the average price per squarefoot of the comparables and multiplying it with the squarefootage of the property to calculate the ARV? Of should I base it primarily on the average sales price for a 3 br 1 Bath?

Thanks