New W4 confusing

I needed to increase my withholding this year but when I went to my employer’s online W4 form, I was surprised to see the format changed. Before I changed the number of people I was claiming and with holding was based on those numbers. Now it’s asking for actual dollar amounts based on calculations. I entered the amounts based on our situation but when my latest paycheck came through, less money is being taken out. I need more taken out. How do I know I’m having enough money withheld? I don’t want to get stuck with a huge tax bill next spring. Is there somewhere I can go to get an estimate of how much tax I should be paying/withholding ? Thanks!