Gravity/Hops Ratio Chart

[d_ozz68]

I'm still sort of a noob here, been lurking for about 4 months and have only recently posted a few times. I have a question regarding the Gravity/Hops Ratio chart that I have seen included with many recipes on the site. Does anyone know if the IBU's listed on the chart are based on the Rager scale or the Tinseth scale?

Any information that anyone could provide would be greatly appreciated........Thank you,

 

[d_ozz68]

.........must be a really dumb question or nobody knows.