Inventory management is a balancing act. Too many of these and too few of those and suddenly your bottom line is shrinking and there’s not enough money coming in to replace what’s going out.It can be particularly tricky when you run a small business. If your margins are already tight, a forgotten case of summer merchandise in a remote storage facility really hurts. Luckily, you don’t need an expensive inventory management system to keep track of it all. You simply need a smartphone or tablet and one of these easy-to-use apps.1. Stock ControlIf you have items stored in a variety of places, Stock Control can help you find what you need fast. The inventory input screen allows you to note an item’s physical location — be it a storage unit on the other side of town or a specific shelf in your warehouse. You can also create your own groupings by size, color or style, so you can easily search, for example, all of the red shirts in stock versus the blue ones. Add quantity and cost and Stock Control will let you know at a glance how much money you have tied-up in each item.Running low? The app can send you a restock reminder. It can also generate a PDF catalog to share internally or with customers via email.Stock Control works on both the iPhone and iPad. It’s free to try for up to 15 items. The full version is $9.99.Related: 3 Mobile Apps to Help You Make Good Habits — Or Break Bad Ones2. On Shelf — Retail Inventory ManagerThis is an iPad app that focuses on optimizing your inventory by monitoring what sells, when and how fast. The app produces sales reports on a daily, weekly or monthly basis. From here you can drill down to see selling trends and which products are returning the most profit.On Shelf then uses the sales trend information to figure out how many of each item you need to keep in stock and when you need to order more. The app even figures in average order lead time on individual items so you won’t run out before the new merchandise arrives.Red, green and yellow status lights make it easy to see where your inventory stands in an instant. You can even use it to place and track your inventory orders and review customer histories.The app sells for $4.99 and requires an iPad running iOS 7 or higher.Related: De-Stress and Unwind With These 3 Free Relaxation Apps3. LettuceIf you’re looking for an app that can handle all aspects of your ecommerce business, Lettuce is all you need. This beautifully designed iPad app not only keeps track of your inventory, but it also functions as a mobile catalog and point-of-sale application. That makes it perfect for trade shows, sales reps and flea market sellers.What really makes this app unique is that it integrates with all of the other online tools you use to run your business such as QuickBooks and all major shipping services. Coming soon is the ability to interface with Etsy, eBay and Amazon so you can spread your inventory out over all the ecommerce platforms without worrying about the double-sell.The app is free with your monthly Lettuce subscription. The service starts at $39 a month, but you’ll need to upgrade to the $89 a month if you want to monitor your inventory online with a 14-day free trial.Related: Mobile Apps to Make Business Travel Easier Register Now » Free Webinar | Sept. 9: The Entrepreneur’s Playbook for Going Global March 27, 2014 Growing a business sometimes requires thinking outside the box. 3 min read Opinions expressed by Entrepreneur contributors are their own.