i’m usin a 20" unicycle at the moment. Thinkin of gettin a new faster one. Should i get a twenty six or twenty four. Will twenty six be to big of a jump from twenty.
Need more info. How well do you ride now. What kind of riding do you like to do and what kind of riding do you want to do on the larger Uni.
Bigger is better. Biggest is BEST! Skip the middle man and go straight for a 36".
If you are short of $
A 26 is the cheapest thing to keep on the road. Folks throw away broken bikes with newish 26 tires all the time. 20’s maybe sometimes, but there are maybe 20x as many good 26 tires in the bin. You will never find a 24x3 muni or 19 cycle tire in the trash in the USA.
It’s a big jump from a 20 to a 36, spending some time on a 24 or 26 muni is a good idea as a step up from a basic 20. Even a plain skinny tire 26 is a good step up from a 20. The fat 3" wide tires are more fun and take less skill to ride, it’s to bad they cost twice the $. I’m not saying you can’t go from a 20 to a 36, just that muni’s are fun, and would be a good next buy. Then of course you have to get a 36 LOL.
If you compare a decent low end muni, like a Nimbus 26, to the cheaper skinny tired 26’s, you can see why it costs twice as much. The tire is twice as fat, the rim is double walled alum and twice as wide. You pay twice as much but you get at least twice the unicycle. Compared to a low end 26, the hub and cranks are not going to break, the frame won’t bend and the seat is 10x better. From there it just gets better, a KH is a little lighter, looks better and has the best seats etc. If you can afford it, a soft tired 24 or 26 muni will roll over stuff and be more fun than a skinny hard tire uni. You need a fat tire to roll across soft soil, it opens up new riding places.
To answer the original question, no, 26" will not be too big of a jump.
But if you really want to go places, consider a 36".
A 24 is 20% bigger, faster, etc. than a 20. That’s a big jump.
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A 26 is 30% bigger, faster, etc. than a 20. That’s an even bigger jump.
But a 26 is only 8% bigger than a 24, so there isn’t that much in it.
(These figures all assume the unis to be exactly 20, 24 and 26 inch diameter, which is seldom the case.)
The step up to 24 would take you a few minutes to “dial in” your balance. The step up to 26 would take a little longer, but not that much longer.
If you can ride your 20 reasonably well, you could do an assisted mount onto any unicycle and ride it on the flat - even a Coker or a giraffe.
A 26 is slightly heavier and harder to steer in a tight space than a 24. A 24 would be more versatile on twisty tracks through the wood. A 26 would be more at home on open trails, and could cope with rougher ground. On the other hand, if you want to hop and jump, the lighter wheel is the way to go.
If you want versatility and contrast, you could consider a 29: small enough to carry or store, big enough to ride serious distance, rugged enough to cope with most trails. And 45% bigger and faster than your 20.
A 24 with reasonably short cranks can be pretty quick, as well as still being small-ish and very manoueverable. Don’t know the difference between that and a 20 though as I’ve never ridden a 20.
If all-out speed is what you want and you’re mainly using your uni for transportation, I’d definitely go with the guys above and say get at least a 26. Less frantic pedalling! I’m sure you;d master it soon enough, it can’t be as hard as learning to ride one of these things in the first place! 
The difference is really noticeable. Get onto a 20 after riding anything bigger, and it feels like a toy for the first few minutes.
For a few months, many years ago, I had a simple cheap 24" and put 102mm cranks on it. I scooted merrily around at fairly high speed, sometimes for an hour at a time without a dismount. On another occasion, I rode 24 miles in a day on it.
thnx for the help
think i will go for the 26" wheel, but it sounds like the 36" is fun so i will have to got one of them sumtime. thnx for the help