Why SGD Is So Fast (One Epoch, Thousands of Steps) Why is Stochastic Gradient Descent often faster than Batch Gradient Descent? The key difference is simple: Batch Gradient Descent computes one update after summing over all data points. SGD removes that sigma and updates the weights using just one data point at a time. That means if you have 10,000 data points, SGD updates the weights 10,000 times in a single epoch. As this animation shows, SGD often reaches near-optimal regions very quickly—som