There isn't actually a cap. Q: What happens if I go over my data budget? A: Project Fi will first alert you if you're getting close to your data budget. If yo

There isn't actually a cap. Q: What happens if I go over my data budget? A: Project Fi will first alert you if you're getting close to your data budget. If you go over, you'll still get full-speed data and data is charged at the same $10 per GB rate. For example, if you go over your data budget by 350MB, $3.50 will be added to your next bill." source: https://fi.google.com/about/faq/#plan-and-pricing-4 https://fi.google.com/about/faq/#plan-and-pricing-4