Yorkshire pudding should be made by ingredients of equal volume, not weight. I use one of those measuring cups which that come as a set of four in different sizes. 1 cup, half cup, 1/3 cup and 1/4 cup.

For a decent sized pudding (10" x 8" roasting tin) use:

1/2 cup plain flour
1/2 cup eggs
1/2 cup semi-skimmed milk
pinch of salt.

Fill cup with plain flour and level off top. Put flour into a decent sized bowl and then add salt.
Fill cup with eggs (around 2 is average) and after making a well in the flour, pour in the eggs.
Using a balloon whisk, lightly beat the eggs and then begin to incorporate the flour a bit at a time, until a thickish batter is produced.
At this stage fill your cup with the milk and add a little to the batter to slacken it. Keep beating the batter incorporating more flour and milk a bit at a time before finally adding the remainder of the milk.
Continue to beat the batter mix with the whisk to get some air into it, this will help it rise.
Place your chosen fat into your roasting tin - enough to cover the base. I use 1 x tbs. duck or goose fat. Coconut fat will do at a pinch or even sunflower oil. Don't use olive oil because it will burn.
Place your roasting tin in the middle shelf of a pre-heated oven at around 200degc and leave it alone for a good 15 mins or so.
When you're ready, give your batter another whisk and pour into the tin. The batter should sizzle around the edges as you pour it in.
Close the oven door, turn the temp down to around 180degc and forget about it for at least 12mins (I have a fan assisted electric oven, so you may have to adjust this time). After that time open the oven door slightly to check. If you have a glass door, even better. When the pudding is well risen, take it out and scoff it.