We calculate the difference between the dulled and sharpened knife to see how effective the knife sharpener has been. Jason Horn, a commerce writer for The Spruce Eats, updated this roundup to include data from our extensive tests of 22 sharpeners—10 electric and 12 manual—by both freelance testers and in our Lab in Birmingham, Alabama.

We did not expect a knife sharpener at this low of a price to work as well as it does, but the Longzon 4-in-1 really delivers. As the name suggests, the manual sharpener has four slots—three successively finer ones for standard knives and an extra-wide one especially for sharpening scissors and shears. Some manual sharpeners take a little practice to use correctly, but the Longzon's design and included directions make things simple. There's even a QR code link to video instructions if you're more of a visual learner. It doesn’t matter which knives you buy—they'll all need to be sharpened periodically. Besides making it easier to cut and chop, keeping knives sharp is also safer for your fingers: Dull knives can drag or skip while cutting, which can increase your chance of injury. How often you need to use a knife sharpener depends on exactly how often you use the knife, what you cut, and what surface you cut on, but professionals typically recommend sharpening once or twice a year. Manual sharpeners are generally cheaper and simpler to use, but they require more effort, so they may not be ideal for people with limited hand grip or arm strength. They're easier for a beginner to use correctly compared to an electric knife sharpener. A honing steel, sometimes also called a honing rod or a sharpening steel, doesn't exactly sharpen your knife. Instead, it realigns the cutting edge to smooth out microscopic bumps and jagged edges. Handheld manual knife sharpeners are designed to keep your blade fresh, and you should use them to top up the blade after every few hours of use. An electric knife sharpener or whetstone would be your best bet for a fully dulled knife.We choose the most popular manual and electric knife sharpeners available at UK retailers to test. We buy all the products we test and rate them on the two factors below. Sharpening ability To discover the best knife sharpeners on the market, we collected an array of dull knives—plus several boxes of Band-Aids—and tested their performance slicing through paper, carrots, and tomatoes (and a baguette, for serrated blades), both before and after sharpening. We also measured each knife's sharpness scientifically, using an Edge-on-Up tool to record the exact amount of force needed to cut through a standard material.

Keeping it at that angle, pull the knife down the honing steel while pulling the handle towards you.A whetstone combined with a honing steel gives the best results (better than knife sharpeners). But (and it's a big but) only use this method if you know what you're doing. Otherwise, you risk damaging the cutting edge of your knife.

We then sharpen the knife with its dedicated knife sharpener according to the manufacturers' instructions. German company Wüsthof has been making world-famous knives for more than 200 years, so it makes sense that its sharpening tools are also high-quality. The Easy Edge features a spinning belt that runs at three separate speeds for coarse honing up to final polishing, along with a one-touch program with indicator lights for each stage. An integrated suction fan also keeps dust out of the way. How easy or difficult the sharpeners were to operate: We tested both manual and electric sharpeners, noting their learning curve and ease of control. We also appreciated the models that came with easy-to-follow directions and video instructions. Each knife sharpener will have its own specific directions, and you should always follow those, but in general, you insert the blade into the slot and pull it through with even pressure several times. It's important to make sure the full blade passes over the abrasive, all the way from heel to tip. Then, you repeat the process on the other side of the blade (though some sharpeners work on both sides at once), first using the coarsest slot and then each of the finer ones. The electric Chef'sChoice 130 Professional Sharpening Station is simple to use and works well on many different sizes of blades, while the manual Longzon 4-in-1 offers similar quality with a low price tag. For those on a budget, the electric Presto EverSharp is excellent, too. How We TestedFinish with a honing steel for best results. Rinse and dry the knife. You may also need to clean up the area around the whetstone. Pull the knife blade along the sharpening steel towards you, with enough gentle force that you can hear a grinding noise. Hold the knife at about a 22-degree angle to the stone. 90 degrees is your knife placed on the stone as if you were going to cut through it. Tilt the knife halfway between that and the whetstone and you'll be at 45 degrees. Then tilt it halfway between that and the stone, and you'll be at around the correct angle you need. Brod & Taylor Professional Knife Sharpener: It looks like a piece of contemporary sculpture, and its maker claims that its spring-loaded design is foolproof to use, but we had to manually hold the unit open to insert the knife and weren't able to get very good sharpening results at all. Add a hefty price tag, and you've got a sharpener we wouldn't recommend. A brand-new knife has (in theory) a perfectly straight blade, ground down to a precise cutting edge at a specific angle. As you use it, the metal on the edge gets damaged on a microscopic level, causing uneven spots that can get caught on foods and create a ragged tear rather than a clean cut. A sharpener does for a metal knife basically the same thing that sandpaper does for a wooden board: It shaves off a layer of uneven material to make the surface smooth and even again. Different models of sharpener use different materials and methods to remove metal, along with different methods of holding the knife in the correct position while doing so.