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I'm looking at getting a new blender, basically the main things I want to be able to do with it are make curry pastes, ultra smooth restaurant quality purees and soups and grind small amounts of spices (I'm talking 1-2 teaspoons). This leaves me with two choices (possibly three of which I'll get too): the Blentec or the Vitamix. The former goes to 27,000rpm and the latter goes to 37,000. I'm wondering is there much of a difference once you get up to crazy speeds like that.

The other option is a Thermomix, which from my reading only hits speeds of 11,000rpm. Unfortunately, given that many Thermomix owners also sell them, it's pretty hard to get unbiased information online so I'm wondering if a speed drop of nearly two thirds will make a difference to the smoothness of my purees. From demos I've seen it think the Thermomix will do a better job with curry pastes and spice grinding as the blades nearly touch the base of the container unlike the other two units: my thinking being that however high the rpm of the Vitamix/Blentec, if the teaspoon of spices can't come into contact with the blades, it's useless.

I read the What to look for when purchasing a blender? question and found no mention of rpm so maybe it's a parameter that isn't very useful, if so then it would be nice to know that at least.

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  • I believe this answer is most accurately described as 'it's hard to find a blender that doesn't easily hit the maximum RPM you are likely to need, thus it is not important'. I only suspect, not know, so I'm just commenting.
    – Myrddin Emrys
    Mar 30, 2012 at 3:06
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    tiny spice grinder might be best bet (why stain up blender anyway?)
    – Pat Sommer
    Apr 1, 2012 at 2:15
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    speed is nice but less so than a cool running motor that can go 30min -how restaurant kitchens get super smooth results (they also strain)
    – Pat Sommer
    Apr 1, 2012 at 2:17
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    I seriously doubt any blender will be successful in grinding two teaspoons of dry spices. The blades would have to be so close to the bottom of the container as to be useless for most other things, unless the container was so narrow at the bottom that two teaspoons would fill it. Blenders work on a vortex that is usually liquid-based so a blender is probably the wrong tool.
    – Wayne
    Sep 12, 2019 at 22:52
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    High speed blenders levitate small amounts of solids, like your spices. Running them dry also heats up the bearing or bushing, or whatever is holding the blades in position. That increases wear, and burnout of the blade assembly. All the high speed, 20-30Krpm, blenders I've seen are designed with liquids in mind. Two minutes with dry seeds on my Ninja, with an old, and wobbly blade will make smoke in the blending chamber, as solids work their way into the bearing, and heat to ignition temp. Grinding dry stuff is the very best way to wreck a high speed blender blade assembly. Use Spice Grinder!
    – Wayfaring Stranger
    Sep 12, 2019 at 23:39

6 Answers 6

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I've used both a Vitamix 500 (not extensively) and a Thermomix TM31. I didn't know there was a difference in RPM, but I didn't notice too much difference in end-effect when both were turned up to full power. So I think it doesn't make much difference at those speeds anymore.

If you're having trouble milling spices though, it helps to heat them a while in the oven, to get rid of humidity and therefore make them more brittle.

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  • With a 1 inch (25mm) radius blade, the 27kRPM blender is pulling 20412 g units at the blade tips, while the 37kRPM unit pulls 38332 times gravity. msu.edu/~venkata1/… That later value is enough to make me wonder about the bearing lifetime of the unit. 25kRPM is enough for routing wood, it should be enough for pureeing foods. highlandwoodworking.com/variablespeedrouteradvice.aspx
    – Wayfaring Stranger
    Apr 6, 2012 at 13:40
  • Has the Thermomix longer blades than the Vitamix? So the speed (and gravity pull) of the Thermomix might be similar to the vitamix?
    – Sam
    Jan 30, 2014 at 11:37
  • The thermomix is afaik stronger than the vitamix. What I know for certain is that it is built with very high quality and will last a long time. The motors are still manufactured in Germany.
    – Steve Heim
    Jul 24, 2014 at 19:21
  • With sharper blades, you don't need as many g's to make the cut. I remove, left handed thread, and sharpen the blades on my Krups coffee grinder. Have not yet done so with my 20krpm blender, but being off balance by a gram makes a lot more difference in high rpm devices. Also, blender blades are not usually constructed with easy balancing in mind.
    – Wayfaring Stranger
    Sep 13, 2019 at 23:39
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RPM is an important factor when selecting a blender, but it's not necessarily the most critical. A blender with high RPM will blend faster, but it may not actually be indicative of how well the blender blends. In general, a powerful motor is more critical than one that simply spins fast. The higher the horsepower, the more consistently the blender will be able to run after continuous use. The torque of the blade/motor is also an important factor to consider. Higher torque means that the blade will be less likely to stop or slow upon impact with tough or dense items like banana slices or chunks of pineapple.

So while RPM is definitely important (you obviously don't want a blender that takes forever to blend up your food), it's not the only determining factor. Most professional-grade blenders will have much higher RPM ratings than standard residential blenders, but at the professional price level, horsepower and torque are just as important when making your decision.

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  • I see you are the author of the linked to article that reads like an advertisement for a certain brand. I downvoted this as it reads like an advertisement for that product.
    – dpollitt
    Jun 11, 2016 at 4:40
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I've been researching blenders and realize this is old thread but just adding what I found. It seems operating horsepower(torque) is the main criteria to focus rather than RPM. A bunch of blenders advertise peak horsepower but the blenders don't sustain peak horsepower when they are blending. RPM seems to matter once the ingredients are blended. Cnet had a decent article explaining HP for blenders https://www.cnet.com/how-to/the-truth-about-horsepower-in-blenders-and-food-processors/

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  • Ideally you want rpm to be independent of load. In the real world, achieving that will result in tripped breakers or burnt motor coils.
    – Wayfaring Stranger
    Sep 13, 2019 at 23:45
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RPM is an important factor. Although it blends the food more smoothly and much faster if it has a higher RPM, it also uses more power and does not blend harder objects as efficiently/well. Although it is important, it is definitely not the most important factor when choosing a blender. If you have the power supply, I definitely reccomend having a high RPM blender.

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The higher RPM is better. Provided you can control that from the lowest RPM to its Highest. The kind of stuff you want to mix will determine the correct RPM to use.

The torque is also important. This means for a layman point of view the strength of your motor. Example: You are to mix a thick dough, would your motor sustain the mixing at a given RPM? If your RPM slows down, it means your motor cannot sustain the RPM given the thickness of the dough.

Chef has a feeling of the performance of their mixer motors, however I doubt if they can tell at what RPM their mixer runs.

The speed of mixers let us say, 5 speed. The manufacturer should indicate the RPM of speed 1= 450rpm, speed 3, 550 rpm, speed 3= 650 rpm etc..(only an example figures but not the actual so you may understand)

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Higher RPM is better for smoothies. If you've ever been to Jamba Juice or some other smoothie shop, that great texture mostly comes from the high RPM of the blender

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    How do you know it is because of the RPM of their blenders and not, say, the torque of the professional blenders' motors or the sharpness of their blades?
    – rumtscho ♦
    Apr 3, 2012 at 9:41
  • @rumtscho good point
    – Geore Shg
    May 5, 2012 at 4:01

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