# Tinseth IBU Formula

### Help Support Homebrew Talk:

#### LS_Grimmy

##### Well-Known Member
Anyone know what the e^ in this formula is?

utilization = (1.65 * 0.000125^(wort gravity - 1)) * (1 - e^(-0.04 * time in mins) )
(---------------------------- )
( 4.15 )

#### david_42

##### Well-Known Member
e is the base for natural logarithms. Use 2.72

OP

#### LS_Grimmy

##### Well-Known Member
thanks man i owe you one... figured out that formula for my excel sheet and let me tell you it wasn't easy to get some of those figures to work with excel

#### Beerrific

##### Well-Known Member
In Excel you can use "exp(--)" for the exponential.

OP

#### LS_Grimmy

##### Well-Known Member
Beerrific said:
In Excel you can use "exp(--)" for the exponential.
Thanks I actually just did this:

Utilization = (1.65*0.000125^(OG-1))*((1-2.72^(-0.04*Hop Boil Time))/4.14)

IBU = Utilization *(oz*(AA% / 100)* 7490) / Volume of Batch in Gallons

Thanks for your help. I got it to work perfectly in excel. I just like playing around with these math formulas

Cheers
Grimmy