Feel free to tell them what you make just add 15-40% to that number. This has worked well for me. Employers seem happy as well.
Example:
Assuming your current salary is X.
"So I currently make (X * 1.20), but in order to make the jump I need at least (X * 1.40)."
That way they get to feel out immediately whether they can afford you, you get the salary that would motivate you, and no one is wasting time in the hiring process.
Keep in mind many employers wont want to pay you more than 8-10% more than what you "currently make" unless they are incredibly motivated to hire you and you alone.
Example:
Assuming your current salary is X. "So I currently make (X * 1.20), but in order to make the jump I need at least (X * 1.40)."
That way they get to feel out immediately whether they can afford you, you get the salary that would motivate you, and no one is wasting time in the hiring process.
Keep in mind many employers wont want to pay you more than 8-10% more than what you "currently make" unless they are incredibly motivated to hire you and you alone.