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A large countertop oven can save time only when it cooks enough food, heats quickly, and does not create more cleanup than your full-size oven. The Ninja Prestige Smart XL Air Fryer & Countertop Oven with Pro Cook System, model DT551, combines two-level convection cooking, 10 functions, and an included food thermometer in one stainless steel appliance. Its main strengths are fast preheating, broad cooking space, and automatic doneness control for proteins. Its main tradeoffs are a wide countertop footprint, a 33.62-pound body, and accessories that need hand washing.
Quick Verdict
Rating: 9.2/10, Recommended
Best For: Families and frequent home cooks who want two-level meal preparation, fast preheating, and thermometer-guided roasting.
Bottom Line: The Ninja Prestige Smart XL DT551 offers useful cooking space, 10 clearly defined functions, and a Pro Cook thermometer that can stop the heating cycle at your selected internal temperature. It is a strong daily alternative to a full-size oven, but you need enough permanent counter space and time for hand cleaning.
| Specification | Detail |
|---|---|
| Brand | Ninja |
| Model | DT551, DT550 Series |
| Product Type | Air fryer, convection toaster oven, and countertop oven |
| Cooking Functions | Air Fry, Whole Roast, Air Roast, Bake, Dehydrate, Pizza, Broil, Toast, Bagel, and Reheat |
| Heating System | Smart Surround Convection with two-level cooking |
| Preheat | 90-second oven preheat stated by Ninja |
| Stated Food Capacity | Up to two 9 x 9-inch pans, 20 cookies, 9 toast slices, or a 12-pound turkey |
| Dimensions | 19.84 in L x 17.09 in W x 13.35 in H |
| Weight | 33.62 lb |
| Power | 1,800 watts, 120 volts, 15 amps |
| Material | Stainless steel exterior |
| Cord Length | 36 inches |
| Included Accessories | Air fry basket, 2 sheet pans, 2 wire racks, removable crumb tray, Pro Cook thermometer, and recipe/cooking guide |
| Cleaning | Dishwasher-safe use is not supported; follow the guide and hand wash the accessories |
| Warranty | 1-year limited warranty |
What Is the Ninja Prestige Smart XL DT551?
The Ninja Prestige Smart XL DT551 is a wide countertop convection oven designed to handle air frying, roasting, baking, toasting, broiling, reheating, pizza, and dehydrating. It is not an 8-quart basket air fryer. Ninja describes its capacity by the food and cookware it can hold, including two 9 x 9-inch pans, 20 cookies, nine slices of toast, or a turkey weighing up to 12 pounds.
The oven uses Smart Surround Convection to move hot air around food on one or two rack levels. Ninja states that you do not need to flip food or rotate the racks when the correct function and rack positions are used. That design is useful when you want to cook a main dish and a side at the same time without preparing two batches.
The DT551 also includes the Pro Cook System with an Auto Temp Detect thermometer. You insert the probe into the thickest part of a protein, choose a food type and doneness level or set a manual target, and start cooking. When the probe reaches the selected target, the oven stops the heating cycle and alerts you.
Who Should Buy It?
Best For
- Families that regularly cook sheet-pan dinners, several portions, or a main dish with a side
- Home cooks who want a thermometer-guided way to roast poultry, pork, beef, lamb, or fish
- Buyers who want one appliance for air frying, baking, reheating, pizza, toast, and dehydrating
Skip If
- Your counter cannot hold an appliance about 20 inches long and 17 inches wide with ventilation space around it
- You mainly cook one small portion and would rather use a compact basket air fryer
- You want dishwasher-safe trays and baskets with minimal cleanup
Feature-by-Feature Review
10 Cooking Functions
The control panel gives you 10 programs: Air Fry, Whole Roast, Air Roast, Bake, Dehydrate, Pizza, Broil, Toast, Bagel, and Reheat. The list covers most daily countertop-oven jobs without using vague combination modes. Toast and Bagel also let you choose the number of slices and a browning level, while the roast and bake modes handle larger foods and pans.
The main limitation is that presets still require attention when you use a new recipe. Food thickness, starting temperature, pan material, and crowding can change the result. Check food early until you know how your usual recipes behave in this oven.
Smart Surround Convection and Two-Level Cooking
Smart Surround Convection is the DT551’s main performance feature. Heated air circulates around the racks to support even browning across two levels. The oven includes a dedicated 2 LEVEL setting, which adjusts the cooking setup for food placed on both rack positions.
This is most useful for foods that need similar temperatures, such as chicken pieces with vegetables or two trays of cookies. It does not let you run two different temperatures at the same time. You also need to follow the rack chart for the selected function because airflow and distance from the heating elements affect browning.
Pro Cook Thermometer and Automatic Doneness Control
The included thermometer adds more value than a basic countdown timer. Preset food types cover fish, chicken, turkey, pork, beef, and lamb, with doneness choices where appropriate. You can also use manual mode to set a target internal temperature.
For a reliable reading, place the probe horizontally into the center of the thickest part of the food. Keep the tip away from bone, large pockets of fat, and the pan. The oven displays the current probe temperature and target, then stops and shows “COOK END” when the target is reached. Ninja still advises checking safe food temperatures with a separate food thermometer.
XL Cooking Space Without a Quart Rating
The DT551 is built around flat racks and pans, so a quart number would not explain its useful space. The more helpful capacity claims are two 9 x 9-inch pans, 20 cookies, nine slices of bread, nine bagel halves, or a turkey up to 12 pounds. That space suits families better than a small basket that forces food into a deep pile.
The tradeoff is exterior size and weight. At 33.62 pounds, it is better treated as a permanent countertop appliance than something you move in and out of a cabinet each day.
1,800-Watt Heating and 90-Second Preheat
Ninja lists a 90-second oven preheat time and a 1,800-watt heating system. That short warmup can reduce total meal time compared with waiting for a large range oven. It is especially helpful for frozen foods, small bakes, reheating, and weeknight roasting.
Preheating is only one part of total cook time. A crowded oven or a large cold roast can still take longer than a small batch. Leave space around food so moving air can reach the surfaces you want to brown.
Stainless Steel Build and Included Accessories
The stainless steel exterior gives the oven a clean, full-size-appliance look. Ninja includes two wire racks, two sheet pans, an air fry basket, a removable crumb tray, the Pro Cook thermometer, and a recipe and cooking guide. The two-rack set is important because it lets you use the oven’s full two-level design without buying a second rack.
The controls and body become hot during use. Use the door handle and insulated oven mitts when moving pans, racks, or the thermometer. Do not place items on top of the oven while it is operating.
How It Performs in Real Use
For Quick Weeknight Meals
The fast preheat and broad sheet-pan layout are a good match for chicken pieces, salmon, vegetables, frozen snacks, and reheated leftovers. You can spread food in a single layer instead of stacking it in a basket, which gives steam more room to escape. That setup is useful when crisp edges matter.
For Two-Level Family Cooking
Two-level cooking reduces the need for back-to-back batches. You can prepare a protein on one level and a side on the other when both work at the same temperature. Select 2 LEVEL and use the rack positions shown for the cooking mode. Avoid packing either tray so tightly that airflow is blocked.
For Roasts and Whole Poultry
The Whole Roast function and Pro Cook thermometer are helpful for larger proteins. The automatic target feature reduces repeated door opening, which can release heat and extend cooking time. Correct probe placement still matters, and you should confirm the final temperature with a separate food thermometer before serving.
For Toasting, Baking, and Dehydrating
The nine-slice toast capacity works well for family breakfasts. Bake handles cookies and small pans, while Dehydrate uses lower heat over a longer period for fruit, herbs, or jerky. Dehydrating results depend on even slice thickness and spacing, so do not overlap pieces.
Setup, Rack Placement, and Safety
Place the oven on a level, clean, dry countertop away from the edge. Ninja’s owner guide calls for at least 1 inch of open space above and on all sides for air circulation. Keep the vents clear, do not place the unit on a stovetop, and do not use an extension cord.
Install the crumb tray below the lower heating elements, not in a rack slot. Do not cover the crumb tray or heating elements with foil because trapped heat can create a fire risk. Use the supplied accessories or properly rated oven-safe cookware that fits without touching the elements.
Pro Tip: Before the first full meal, use the rack guide to test one familiar food. Note the rack level, mode, temperature, and time so you can repeat the result without guessing.
Before You Buy: Measure the counter, nearby wall space, and cabinet height using the oven’s 19.84 x 17.09 x 13.35-inch dimensions. Add at least 1 inch above and on every side for ventilation, and remember that the door and exterior surfaces become hot.
Cleaning and Maintenance
The DT551 is not a dishwasher-safe appliance. Unplug it and let it cool fully before cleaning. Slide out and empty the crumb tray, then wipe the interior walls and glass door with a soft, damp sponge after each use. Frequent wiping is easier than removing baked-on grease later.
Ninja recommends hand washing the accessories. The sheet pans and crumb tray should not go in the dishwasher, and the thermometer should be wiped with a damp cloth rather than immersed in water. Keep liquid cleaner away from the thermometer jack. Use non-abrasive tools so you do not damage the cooking surfaces or glass.
Pros and Cons
Pros
- 10 practical cooking functions cover air frying, roasting, baking, pizza, toast, and more
- Two-level convection cooking can prepare larger family portions in one cycle
- Pro Cook thermometer tracks internal temperature and stops at the selected target
- 90-second stated preheat reduces waiting before many everyday meals
- Includes two racks, two sheet pans, an air fry basket, crumb tray, and thermometer
Cons
- The wide body and 33.62-pound weight make it hard to store between uses
- Accessories require hand washing, and greasy foods can create frequent cleanup
- Two-level cooking uses one shared temperature, so foods must have compatible cooking needs
Is It Worth the Price?
The Ninja Prestige Smart XL DT551 sits in the premium countertop-oven category. Its value comes from replacing several common appliances and adding features that basic toaster ovens often lack, especially two-level convection cooking and an included doneness thermometer.
It is worth considering if you cook for several people, use a countertop oven most days, or want to avoid heating a full-size oven for routine meals. It is less compelling for a one-person kitchen, a very small counter, or anyone who values dishwasher-safe cleanup more than capacity and versatility.
How It Compares to Alternatives
A compact basket air fryer is easier to store and may crisp a small serving faster, but it cannot match the DT551’s flat cooking area or two-rack setup. The Ninja Flip Toaster Oven is a better fit when saving counter space is the main goal because it folds upward when not in use, but it has fewer functions and less permanent cooking volume.
Premium Breville and Cuisinart air fryer ovens are also worth comparing for control layout, interior shape, and accessory care. The DT551 makes the most sense when the included Pro Cook thermometer, two-level cooking, and stated 90-second preheat matter more than compact storage.
Frequently Asked Questions
Is the Ninja Prestige Smart XL an 8-quart air fryer?
No. The DT551 is a rack-style countertop oven, and Ninja does not list its capacity in quarts. Its stated food capacity includes two 9 x 9-inch pans, 20 cookies, nine toast slices, or a turkey up to 12 pounds.
What are the Ninja DT551 dimensions?
Ninja lists the oven at 19.84 inches long, 17.09 inches wide, and 13.35 inches high. Leave at least 1 inch of open space above and on all sides, and measure with the door area and nearby cabinet clearance in mind.
Does the Pro Cook thermometer stop the oven automatically?
Yes. After the probe reaches the selected target temperature, the oven stops the heating cycle, beeps, and displays “COOK END.” Use correct probe placement and confirm safe serving temperatures with a separate food thermometer.
Can it cook on two levels at the same time?
Yes. Use the 2 LEVEL setting and the rack positions listed for your chosen mode. Both levels share one temperature, so choose foods with compatible cooking needs and avoid blocking airflow.
Which cooking functions are included?
The 10 functions are Air Fry, Whole Roast, Air Roast, Bake, Dehydrate, Pizza, Broil, Toast, Bagel, and Reheat. Toast supports up to nine bread slices, and Bagel supports up to nine halves.
Are the trays and air fry basket dishwasher-safe?
Ninja lists the appliance as not dishwasher-safe and recommends hand washing the accessories. The sheet pans and crumb tray should not be placed in a dishwasher, and the thermometer should only be wiped with a damp cloth.
What comes in the box with the DT551?
Ninja lists an air fry basket, two sheet pans, two wire racks, a removable crumb tray, a Pro Cook thermometer, and a recipe and cooking guide. Check the seller’s package details before ordering in case a bundle differs.
How long is the warranty?
Ninja lists a one-year limited warranty for the DT551. Keep your receipt and review the warranty terms for coverage limits, registration steps, and service instructions.
The Bottom Line
The Ninja Prestige Smart XL DT551 is a strong choice for families and frequent cooks who want two-level convection space, 10 cooking functions, and thermometer-guided roasting in one appliance. Skip it if your counter is tight, you cook only small portions, or you want dishwasher-safe cleanup. Its best features are usable rack space and automatic doneness control, while its main limitation is the large, heavy body.
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