Net income is the "bottom line" of the income statement. The SEC's guide to financial statements says that "net profit is also called net income or net earnings" and that it is what remains after operating expenses, interest and income tax are deducted. A negative result is a net loss.
Formula
net income = revenue − cost of goods sold − operating expenses − interest − tax
Example
Revenue of $12,500, cost of goods sold of $4,500, operating expenses of $3,600, interest of $400 and tax of $1,000 leave 12,500 − 4,500 − 3,600 − 400 − 1,000 = $3,000. Divided by revenue it is a net profit margin of 24%.
Net income vs gross profit
Gross profit subtracts only direct costs, so it is larger. The profit calculator computes profit after fixed costs and tax, and how to calculate profit margin explains each step.