What this converter works out
Takes the cooking time from an oven or hob recipe and gives the equivalent on a slow cooker's low and high settings, along with the liquid adjustment.
The liquid is the part most conversions miss. A slow cooker is effectively sealed and loses almost nothing to evaporation, so a recipe written for an oven will finish watery unless you cut the liquid by around a third.
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Before you convert
- Slow cookers suit dishes with liquid and time: casseroles, stews, curries, pulled meats, soups and beans.
- They do not brown. Searing meat and softening onions in a pan first makes a substantial difference to the finished flavour.
- Reduce the liquid. A sealed slow cooker loses almost nothing to evaporation, so a recipe written for an oven will end up watery if you use the full amount.
Raw and undercooked red kidney beans contain a natural toxin that slow cooking does not reliably destroy, because the temperature stays too low. Soak them, then boil hard for at least ten minutes before they go anywhere near a slow cooker. Tinned beans are already processed and are safe to add directly.
How this converter works
There is no exact formula, because slow cookers vary and the setting is a rough one. The conversion below follows the bands in common use:
| Oven or hob | Slow cooker, high | Slow cooker, low |
|---|---|---|
| 15 to 30 minutes | 1½ to 2 hours | 4 to 6 hours |
| 30 to 60 minutes | 3 to 4 hours | 6 to 8 hours |
| 1 to 3 hours | 4 to 6 hours | 8 to 12 hours |
The low setting is not a lower final temperature than high. Both settle at around the same simmering point; low simply takes longer to get there. That is why low suits tougher cuts, which need time for connective tissue to break down, and why the two settings are roughly a factor of two apart.
Worked example: a 90-minute casserole
- Oven time of 90 minutes falls in the one to three hour band
- Slow cooker: 4 to 6 hours on high, or 8 to 12 hours on low
- Liquid: reduce 500 ml to about 330 ml
- Brown the meat and soften the onions in a pan first, then transfer
For a tough cut such as shin or shoulder, choose the low setting and the longer end of the range. Time is what breaks down the collagen that makes those cuts worth using.
What to add when
- At the start: root vegetables, tough cuts, pulses, stock. Root vegetables take longer than meat, so put them at the bottom where it is hottest.
- Last hour: softer vegetables, pasta, rice.
- Last 30 minutes: cream, milk, yoghurt and soft herbs, all of which split or lose their character over long cooking.
- At the end: lemon juice, fresh herbs and most of the seasoning. Flavours concentrate less in a sealed pot than in an oven, so a slow-cooked dish often needs more seasoning than you expect, added late.
Common mistakes
- Using the full amount of liquid. The most common cause of a watery slow-cooked dish.
- Lifting the lid. Each look costs roughly 20 minutes of cooking time.
- Skipping the browning. Slow cookers cannot brown, and the flavour that browning creates simply will not appear later.
- Adding dairy early. It splits over long cooking. Stir it in near the end.
- Filling it too full or too empty. Between a half and two thirds full is the usual guidance.
- Using dried kidney beans without boiling them first. A genuine safety issue, not a matter of texture.
Frequently asked questions
Is low half the temperature of high?
No. Both settings reach roughly the same temperature, a gentle simmer. Low simply takes longer to get there and holds it more gently. That is why the two are about a factor of two apart in time rather than being different heats, and why low suits tough cuts that need hours rather than degrees.
How much should I reduce the liquid by?
About a third for most recipes. A slow cooker is effectively sealed, so almost nothing evaporates, while an oven casserole loses a good deal over a couple of hours. If the finished dish is still too thin, take the lid off for the last half hour on high, or stir in a little cornflour slaked in cold water.
Can I leave a slow cooker on all day?
They are designed for it, and long unattended cooking is the point. Follow the manufacturer's instructions, stand it on a heatproof surface away from anything that can catch, and do not fill it above the maximum line. Do not use one to reheat food that has already been cooked and cooled — it heats too slowly, and the food spends too long in the 5 to 63°C range where bacteria multiply.
Why do I need to boil kidney beans first?
Dried red kidney beans contain a lectin that is destroyed only by vigorous boiling. A slow cooker does not get hot enough to do it reliably, and undercooked beans can cause severe sickness. Soak them, drain, then boil hard for at least ten minutes before adding them. Tinned kidney beans have already been through that process and can go straight in.
Should I brown meat before slow cooking?
It is worth the extra pan. Browning creates flavour compounds that a slow cooker cannot produce at its temperature, and no amount of time will generate them later. The same applies to softening onions. It is the single biggest difference between a good slow-cooked dish and a flat one.
Can I convert a slow cooker recipe back to the oven?
Yes, using the table in reverse, but increase the liquid again by about half as much as you removed, and use a lidded casserole at a low temperature, around 150°C conventional. Check partway through, because an oven does evaporate.
Is what I enter stored?
No. Figures are processed in your browser and never transmitted or retained.
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References
These organisations publish the guidance and figures behind this page.
- Food Standards Agency — cooking safely — core temperature guidance, the 5 to 63°C danger zone and hot holding rules
- Food Standards Agency — UK food safety guidance for home cooks and businesses
Dried kidney beans must be boiled hard for at least ten minutes before slow cooking. Follow your manufacturer's instructions for unattended use.