Saaz alpha %?

I have a recipe for an urquell i want to do this evening and it calls for Saaz all the way through now the problem is it does not state the alpha but as its an american recipe so im guessing they are talking about american saaz with an alpha of between 5-7%
Im in Ireland and all i have to hand is Czech saaz with an alpha of 2.2% so am i right in thinking i just up the amount to match the alpha??
ie. 75g american @ 5% i would use 172.5g of czech @ 2.2%

Seems so, 150g of 2.2% a-a Saaz for 60' gives ~38 IBU.

If you can get it, Sterling might be more effective for your bittering charge.

Thanks. I just went with the Saaz 2.2 and upped everything just realised i only have general dried yeast left so its going to be nothing special anyway