Here is a calculator that Nate Silver and the crew at FiveThirtyEight.com put up a few days ago.
If you select "Follow the Experts" it fills in the numbers based on the teams best guess, and the total is 1182. In other words 55 short. There are many ways for Trump to gain those 55 from the remaining pool that are plausible. For instance, he might get some of the unallocated delegates, who number 125. Getting 1/2 of them would assure him the nomination.
There is no calculator for "Get Ted to 1237" provided, as it's beyond the realm of possibility.
Here is the link.. must have been something wrong when I pasted it...
https://www.conservativereview.com/commentary/2016/04/cruz-and-trump-likely-to-miss-delegate-target