I have posted in the forum before on the subject of Yorkshire Pudding, and I suggest you should use the forum search feature to find my posts and the topics in context with the other helpful recommendations.
Meanwhile I suggest two things:
(1) Fill your pan with water and pour it into a measuring cup and get its measure, and divide by four. Or fill the pan 1/4 full and measure that. One fourth of the pan capacity is what you need for the right amount of batter vs. pan size.
(2) IMO your Yorkshire Pudding must have a heavy amount of pan juices (like from your roast) including fat.