How to get the number of steps until a certain accuracy in keras?
When you train the model using the .fit() call, it actually returns an object called history. Train the model using history = model.fit(x_train, y_train...) instead and then once training is complete, you can access the history.history dictionary to see this kind of info. 

Refer to https://machinelearningmastery.com/display-deep-learning-model-training-history-in-keras/ for more information