A recipe calls for 2 tablespoons of fennel seed. I need to use ground fennel instead, but don't know how much to use. 2T or something else?

The quantity makes a difference too--as well as the other ingredients you are adding. But I still say it is better to add too little than too much.

Grind the 2T, then use that powder. But do watch out that the flavor isn't too strong: fresh ground is nice and potent! It will disperse a LOT more and soak everything with flavor. I'd go with 1T and grind it fresh.

I would be a bit more conservative and use two generous teaspoons to replace 2 Tbs of ground fennel, then add more to taste towards the end of cooking. I find that ground spices release more flavour than whole ones. But that's just me.

Anyone have a scale and some ground and whole spice to see what the actual volume equivalent is? Weigh 2 Tbs whole spice, then find out what volume that weight would be in ground?

When spices are ground the become a little more "fluffy," and take up a little more space. Therefore, the same volume (2T)will contain less of the spice. BUT! that's probably ok! When the spice is ground, more surface area is exposed, and more of the flavor can escape more easily. In fact, I might go with a little less still of the ground than the given amount. Maybe 1-1.5 T.

But can you be a little more specific? What are you making? That might help us know how you should use it.

It would help to know what you’re making, but I would probably use a heaping tablespoon of the ground fennel and see how that tastes. You can always add more if necessary. The freshness of the ground fennel makes a difference too--ground spices lose flavor more quickly than whole spices.