First, SnapXam is an AI-powered math tutor that can give you step-by-step solutions to a broad range of math problems, including calculus. It's got a library of more than 5 million solved problems, a step checker and a math worksheet generator. It works on all devices and offers several subscription options, including premium versions for iOS and Android apps.
Another good option is Wolfram|Alpha, a powerful computational knowledge engine that can provide step-by-step solutions, function plots and statistical calculations for calculus. It's also got a lot of other features across many subjects, so it's a good tool for academics and professionals, too. You can use Wolfram|Alpha through mobile apps, a notebook edition and enterprise products.
If you want a combination of AI technology and live tutoring, Gauth could be the way to go. It offers step-by-step solutions, quick answers and live tutoring for subjects including calculus. The service also comes with other features with its PLUS membership, including unlimited solutions and instant tutoring, so it can be a good homework help option for students.