This handy dandy break-even calculator allows you to calculate the number of units you need to sell for your costs to equal your revenue. If you sell one unit more than the break-even point, then you have made a profit. The break-even point is the very minimum you need to sell to stay in business, because at a very minimum, you must cover your costs. However, profit is the real goal and the more you can maximize profit–the better!
For help thinking through strategies to increase your profit, head over to How much do you need to sell to stay in business?