Four appliances cook most of what comes out of a home kitchen: the oven, the slow cooker, the pressure cooker, and the air fryer. They're usually discussed one at a time, as purchases. This guide treats them as one system — what each does to food, how a time in one translates to a time in another, and how to decide which to reach for on a given evening.
The One Distinction That Organises Everything
Every one of these appliances sits on one side of a single line: whether it cooks food with water or with dry air.
Moist heat — slow cooker and pressure cooker. Food cooks surrounded by liquid or steam. This dissolves collagen in tough cuts and makes them tender, but it can't brown anything, because browning requires a dry surface above the boiling point of water.
Dry heat — oven and air fryer. Hot air surrounds the food, moisture leaves the surface, and the surface browns and crisps. Excellent for texture, useless for breaking down a chuck roast in any reasonable time.
Almost every cooking disappointment involving these appliances traces back to asking one side of that line to do the other's job — expecting crisp skin from a slow cooker, or tender brisket from an air fryer. Within each pair, the appliances are largely interchangeable and times convert predictably. Across the line, they aren't substitutes at all.
What Each One Actually Does
| Appliance | Heat Type | Temperature | Best At |
|---|---|---|---|
| Slow cooker | Moist | 190-200°F Low / 290-300°F High | Unattended braises, sauces that need to reduce |
| Pressure cooker | Moist | ~250°F at high pressure | Beans, stock, tough cuts on a weeknight |
| Oven | Dry | Whatever you set | Large cuts, batches, anything that rises |
| Air fryer | Dry | 350-400°F typical | Small crisp items, reheating, single portions |
The pressure cooker's ~250°F is the outlier worth noticing: it's above the boiling point of water, which no open pot can reach. That single fact is why it compresses an eight-hour braise into under half an hour.
How Times Convert
Within each heat type, conversion is reliable enough to do arithmetic on.
Slow cooker ↔ pressure cooker. Convert the slow cooker time to its High equivalent (1 hour High ≈ 2 hours Low), then multiply those hours by about 6 for pressure cooking minutes. An 8-hour Low braise is roughly 24 minutes at pressure. The pressure cooker converter runs this in both directions, and the slow cooker converter handles oven-to-slow-cooker times.
Oven ↔ air fryer. Reduce the oven temperature by about 25°F and cut the time by roughly 20%; reverse it going the other way. This is a fallback, not a rule — different foods want genuinely different air fryer temperatures, so the measured per-food settings in the air fryer cooking times chart are more accurate than any conversion.
Across the line, there is no conversion. Nothing turns a slow cooker time into an air fryer time, because the two aren't doing the same thing to the food. If you need to cross, you're changing the dish, not the timing.
Which One Tonight?
| Situation | Use |
|---|---|
| Leaving the house for the day | Slow cooker — the only one safe to run unattended for hours |
| Decided on dinner an hour ago, tough cut | Pressure cooker |
| Dried beans or stock | Pressure cooker — dramatically faster, reliable at altitude |
| Sauce needs to thicken and concentrate | Slow cooker — a sealed pot can't reduce |
| One or two portions, want it crisp | Air fryer |
| Reheating leftovers you want crisp again | Air fryer |
| Feeding four or more | Oven — air fryer batching erases its time advantage |
| Whole roast, sheet-pan dinner, anything that rises | Oven |
The Mistakes Each One Invites
Slow cooker: too much liquid. Almost nothing evaporates, so a recipe adapted from the oven usually needs its liquid cut. Dairy and delicate vegetables also break down over eight hours — add them near the end.
Pressure cooker: forgetting the clock isn't the clock. Cooking time starts only once the pot reaches pressure, which takes 5-20 minutes, and release adds 10-20 more. Budget 20-40 minutes beyond the stated time. Liquid often needs to go up, not down, since the pot needs a minimum volume of thin liquid to make steam at all.
Air fryer: overcrowding. This causes more disappointment than any timing error. A packed basket blocks airflow and the food steams instead of crisping. Single layer, space between pieces, second batch if needed.
Oven: trusting the dial. Home ovens routinely run 15-25°F off their setting, and the difference between convection and conventional matters more than most recipes acknowledge. See the oven temperature converter for Gas Mark and old recipe terms.
What Doesn't Change, Whichever You Use
Safe internal temperatures are identical across every method — 165°F for poultry, 160°F for ground beef, 145°F for whole cuts of pork and beef with a rest. No appliance changes them, and a thermometer stays accurate in all of them. The meat temperature guide and the complete meat cooking guide cover the full set.
Altitude is the other constant worth knowing. It affects the moist-heat pair significantly, since water boils cooler as elevation rises, and it affects pressure cooking mildly. It doesn't affect oven roasting or air frying at all, because dry heat runs well above boiling either way. The high altitude cooking calculator works out the adjustments for your elevation.
Every Related Tool and Guide, in One List
- The Complete Leftover Reheating Guide
- The Complete Vegetable Roasting Guide
- Slow Cooker Time Converter — oven times to slow cooker Low and High
- Slow Cooker to Pressure Cooker Converter — bidirectional, with per-food pressure times
- Air Fryer Cooking Times by Food — measured settings for 13 foods
- High Altitude Cooking Calculator — what elevation changes and what it doesn't
- Oven Temperature Converter — °F, °C, Gas Mark, old recipe terms
- Cooking Time Calculator — times by weight, cut, and method
- Meat Temperature Guide — safe internal temperatures
- Slow Cooker vs Pressure Cooker — which to use for what
- Air Fryer vs Oven — when each one wins
- How to Calculate Cooking Time for Meat
- The Complete Meat Cooking & Temperature Guide