# Calculating bar weight based on volume?

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#### BrianV

##### Member
Is there a way to calculate a bar's weight by volume at cutting time?

I have loafs that are 3 5/8" by 2 1/16". Cutting at 1 1/16" would allow me to get an even 10 bars per loaf, but I want to make sure the final bars are approximately 4oz.

Is there a typical formula for calculating weight based on dimensions that I can work back from? Similar to the '.40' rule for calculating oil weights for molds?

#### Susie

Supporting Member
I can tell you already that you are going to want to have small slivers left on each end. These will not be as pretty as the center bars, and you need some for testing, anyway.

##### Well-Known Member
From everything I have read so far if you are doing CP/HP soaps as they age they can lose some weight. If I have interpenetrated this incorrectly please feel free to correct me. On the other hand from what I read about Melt and Pour soap if you do not package it in some kind of wrap it can attract moisture and increase the weight of the soap and also can end up with dew drops on the surface of the soap.

I would think that this would make a formula for weight by volume hard to figure out if this process is correct.

Todd

#### Seawolfe

##### Well-Known Member
The easy way is to divide the weight of your soap that goes into the mold by the number of bars that width gives you.

#### BrianV

##### Member
The easy way is to divide the weight of your soap that goes into the mold by the number of bars that width gives you.
Yes, I thought about that after the fact. I cut my slab into 10 bars, each 1 1/16" thick and weighing 3.2-3.5 oz. I really can't see going large enough for 4oz bars - this seems (to me) to be pretty close to the ideal size for a 'regular use' bar. I can't see making them 15-25% larger to hit the 'standard' 4oz without becoming a bit unmanageable.

I think I am going to stick with the dimensions I have for this last batch, and not worry about the final weight so much.

#### Seawolfe

##### Well-Known Member
Yes, I thought about that after the fact. I cut my slab into 10 bars, each 1 1/16" thick and weighing 3.2-3.5 oz. I really can't see going large enough for 4oz bars - this seems (to me) to be pretty close to the ideal size for a 'regular use' bar. I can't see making them 15-25% larger to hit the 'standard' 4oz without becoming a bit unmanageable.

I think I am going to stick with the dimensions I have for this last batch, and not worry about the final weight so much.
Yeah I find that I actually prefer smaller bars (2 x 4 x 1), maybe because I have smaller hands, maybe because I like to use my different soaps.

#### SoapSap

##### Well-Known Member
I suggest you trim the ends, weigh the whole loaf, divide the weight of the loaf by the weight you want the bars to be, then evenly cut that many bars.