Depends on the math I suppose, but there are e-liquid calculators online and also available on the iOS Appstore(at least there used to be) and the the Android Play Store.
Usually as simple as
Input Concentrated Nic value
Input Desired Nic Value of juice
Input PG/VG ratio
Input flavoring percentage desired
Input total desired juice size (if you want a 10mL batch, enter 10mL)
Now whether or not you like your creation, thats another story. But if you get into it there are some decent recipes online (google e-liquid-recipesDOTcom)
I'm definitely going to have to look into this more. I didn't realize it could be this cheap. Not to mention that it gives me an excuse to have "lab equipment", and fulfill my inner childs desire to be a "mad scientist" lol
Definitely gonna have to go back to that weird antique shop in my hometown that had glass syringes. Just because they're awesome.