Counting Cals for Juicing

Curious if anyone knows offhand an accurate way to count calories for juicing. I rarely juice, but I had some produce that needed to be used up today. My juice consisted of ... a large bag of kale, about 10 strawberries and 2 lemons. This probably doesn't add up to much at all, but for future reference wondering if there is an easy way to go about calculating juice calories in general.