Guys can you help me out estimating the frame size of this 28" wheel bike
>>973128
Going by the size of the headtube, I'd say it's about 54 cm or 21.25084251968504 in
± 1 or 2 cm though
>>973131
Seconded. Looks like 54.
>>973173
This one is pretty decent. Look up the seat tube size on the left (54cm will be about half way between 20in and 22in, but again 54cm was just an eyeball estimate) then you can see all the relevant lengths and angles for the frame.
Keep in mind, every frame is different and this chart is for one particular frame (no idea what model, just found it of Google images) but it's good to know the different measurements of a frame. If you were meaning what size frame is appropriate for you, then search for “bike frame height chart” or something like that.
>>973173
My advice would be: Always keep frame size in mind when you look at bikes. You will very often find the corret size with descriptions (that is certainly true for new bikes).
With used bikes it is not always reliable, because some people don´t know how to measure frame size correctly.
Over time you`ll get a feeling for the frame size by looking at them.
It is easier with steel frames because they tend to have similar tube diameters.