How Long to Defrost Prime Rib (Food Safe Method)

Larger pieces of meat like a prime rib roast need a longer thawing process.

Which needs to be factored in when planning for your cook. 

Working out approximate thaw times is similar to calculating cooking times.

Part-frozen meat can lead to food poisoning or a spoilt meal.

So make sure you read further and plan.

So how long does it take to defrost a Prime Rib? Let’s find out!


Prime Rib – How to Work Out the Rate of Defrosting

To understand the rate of defrosting there are 2 questions you need to answer.

What is the weight of the frozen beef?
What method are you using to defrost your prime rib?

There are other nuances to cover like safety and if you have a boneless cut or not.

But first, let’s dive into the rate of defrosting!


Rate of Defrosting a Prime Rib in the Refrigerator

A Prime Rib Roast will defrost at a rate of 4-5 hours or 300 minutes per pound.

Rate of Defrosting a Prime Rib in Cold Water

A Prime Rib roast will defrost at a rate of 3-4 hours or 240 minutes per pound.

Rate of Defrosting a Prime Rib in a Cooler

A Prime Rib roast will defrost at a rate of 3-4 hours or 240 minutes per pound.


Example of Defrosting a 6-Pound Prime Rib Roast

The average weight of a prime rib is 4-6 pounds.

At best, you will be waiting a day for a defrosted hunk of meat ready to use in your favorite recipes.

A 6-pound Prime Rib will take 30 hours to defrost in the refrigerator.

A 6-pound Prime Rib will take 24 hours to defrost using the cold water method.

A 6-pound Prime Rib will take 24 hours to defrost using a cooler.


Why It’s a Bad Idea to Defrost Prime Rib in a Microwave

Are you used to quick thawing using a microwave?

This might be fine for smaller cuts before frying on a hot skillet.

But for larger roasts like a prime rib that need a longer cooking time, it is not!

Firstly a whole rib roast probably doesn’t fit in your microwave.

But more importantly, the inside will remain frozen while the outside burns.

It will also create uneven temperature ranges that can cause the growth of bacteria.

More defrosting safety advice later!

Do not try and thaw a whole Prime Rib roast in the microwave.


Guide to Defrosting a Prime Rib in a Refrigerator

We recommend defrosting at a fridge temperature of 37°F.

Refrigerator thawing is the safest method for defrosting meat.

– Organise the bottom level of the fridge for the Prime rib.

– Place in a tray or oven dish large enough for the meat to fit in. (This will catch the water)

– Remove the prime rib from the freezer and straight into the fridge.

– Thaw as per the above timing.

– Check they have thawed completely.

Note: Read further for signs of thawing.


Guide to Defrosting a Prime Rib in Cold Tap Water

Defrosting in a cool water bath in a sink is another viable method.

But you will need to make sure the water temperature stays below 40°F.

– Keep the Prime Rib sealed in the original packaging.

– Fill your sink with cold tap water.

– Submerge the Prime Rib in the cold water bath. (Straight after removing them from the freezer)

– Replace the water every 30 minutes.

– Thaw as per the above timing.

– Check they have thawed completely.

Guide to Defrosting a Prime Rib in a Cooler

Defrosting a large Rib Roast is sometimes easier in a cooler.

It might be because you don’t have fridge space.

Or do you need to safely defrost on the fly before a BBQ while camping?

There is a little more effort when doing this method.

So I have devised aep-by-step guide as below;


Items Required

– A good quality cooler at least double the Prime Rib’s pounds of weight

– Cold water

– Ice packs

– Temperature probes

Step 1 – Clean & Prepare the Cooler

Make sure your cooler is cleaned from previous use.

I reccomend having a specific cooler that you only use for defrosting meat.

This lowers the chance of contamination.

When your cooler is cleaned and ready you can add the frozen Prime Rib.

Step 2 – Put in the Meat & Fill With Cool Fresh Water

– Put the beef in the bottom of the cooler.

– Fill up with cold tap water halfway.

Step 3 – Insert Temperature Probes, Seal the Cooler & Monitor Temp

– Place a temperature probe in the water, away from the Prime Rib.

– Stick a temperature probe at the top of the cooler, out of the water.

– Close the cooler lid.

– Monitor the cooler and water temperatures.

If the probes go above 40°F then add a bit of ice to drop it back down.

If this happens frequently then see below for defrosting in a refrigerator.


How Do I Know My Prime Rib Has Thawed?

There is a difference between thinking your Prime Rib has thawed and being certain it has.

Below are the physical signs to check for thawed raw meat and how to be sure.

Physical Signs a Prime Rib Has Thawed

No ice crystals on the packaging.

– Press the meat to see if it is soft.

– Feel for cold or frozen spots.

Use a Meat Thermometer to Measure the Internal Temperature

The physical signs are a great start.

But I will always reccomend confirming with a food thermometer.

They aren’t just for checking cooked foods!

Using a calibrated instant-read thermometer will give you the exact temperature.

This is the most precise and accurate way of knowing if your meat has thawed.

What Reading Is a Safe Internal Temperature for a Prime Rib?

The safe temperature should be 32°F – 39°F.

Insert the probe into the thickest part of the Prime Rib meat.

Avoid the probe coming into contact if your Prime Rib is bone-in.

Does Having Bone-in or Boneless Roasts Effect Defrostion Rate?

Bones act as conductors for hot or cold temperatures.

In the case of defrosting, having meat with bones may take a little longer to thaw.

This is because the bones hold cold temperatures slightly longer than the proteins.

Don’t worry though as this is very minimal and will only affect the defrosting time by a few minutes.

Plus you can start cooking if the bones are still slightly frozen.

Tips for Freezing a Prime Rib

– Freeze -0°F on the day of purchase in a good quality domestic freezer.

– Freeze in the original packaging.

Do not freeze the Prime Rib for longer than 3 months to avoid freezer burn.

– Figure how much prime rib you need to serve before freezing your meat.

Safety Advice for Defrosting Meat

The ‘Danger Zone’ – Check for Food Safety!

An important one to remember is the temperature range of food-borne bacteria multiplies.

Do not leave any raw or thawing meat at temps between 40°F – 140°F for longer than 60 minutes.

This rule of thumb will lower the chance of contracting an illness.

– Do not use warm water or hot water when defrosting.

– Defrost in the original packaging to avoid contaminating raw meat juices.

– Estimate the timings but use a meat thermometer to be sure.

– Cook on the day the Prime Rib defrosts.

– Look out for signs of spoiled meat.

– Clean the probe you used in raw meat straight away.

Smoke On!


Hi, I’m Charlie, I have been meat-smoking and grilling for the past 15 years. I have an array of different smokers, thermometers, and have a love for finding the right wood and charcoal combo My favourite recipes are my EXTRA CRISPY smoked pork belly, juicy pulled pork, smoked brisket, duck poppers, and ANY SEAFOOD I grill).

I loves sharing his tips with beginners, helping them navigate the world of smoking. I find it’s not just about cooking; it’s a quest for that perfect smoky flavor.

You will usually find me playing with the kids, perfecting my brisket bark, or sipping beers with boys around the fire. Can’t wait to share all my delicious smoking and grilling recipes with you!

You can read more about me on our About Us page.

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