According to 'Tolkien Gateway', their average height is between 4-5' tall but there's no weight range guesstimates. I assume they're pretty well built and muscular, especially the 'warrior class', but I can find no weight charts. A solid healthy weight for a 5' tall human male is about 125 pounds. How stocky are these guys?
Using a very powerfully built 5' tall adult human male and the following description from the Silmarillion, we can arrive at a reasonable guestimate of the body weight of the average healthy adult Dwarf male.
"Since they were to come in the days of the power of Melkor, Aulë made the dwarves strong to endure. Therefore they are stone-hard, stubborn, fast in friendship and in enmity, and they suffer toil and hunger and hurt of body more hardily than all other speaking peoples; and they live long, far beyond the span of Men, yet not forever." ― The Silmarillion, "Of Aulë and Yavanna" http://tolkiengateway.net/wiki/Dwarves<
Considering that a human world class Olympic level power-lifter standing 5' tall (the upper limit of Dwarf height) weighs in at about 140 pounds and that someone 6" shorter (comparable to average Dwarf height) would be comparatively lighter. And factoring in that a Dwarf frame and musculature is likely more dense than a human so we can add back that body mass plus a bit more. The final factor to consider is that Legolas and Gimli doubled-up while riding Arod in their search for Merry and Pippin. Their combined weight was less than if either had doubled up with Aragorn on Hasufel. This leads to the conclusion that though a Dwarf is more 'dense' than a comparable height human, their body weight is not equal to an average size human male.
Based on these factors and the evidence above, and subject to further information or disclosure, it can reasonably be concluded that the average healthy adult Dwarf male weighs in at approximately 150 pounds.
I would go even denser than 150, and say this:
By default dwarves are built stocky, so they are going to have a wider heavily boned frame and extra dense muscle.
Example wise: taking a decent cross-section:
The entire line of Durin as depicted in the films are lean Dwarves. Kili looks half-starved in the promotional pictures. Granted the brothers are barely out of their lanky teen years by dwarf standards. But seriously Kili needs a "sammich". Fili is shorter and more of the standard stocky frame. Thorin although further up the scale as far as being the muscular warrior type, is still very lean VS Dwalin who is massively built like a Biker Bouncer, seriously wouldn't want to be on his bad side! (although wouldn't mind him helping with the round bales...)
The Morian Dwarve cousins, Bifur, Bofur and Bombur, are even shorter and stockier than the royal line. Bifur is 4.5” and would bet in the range of 190lbs , Bofur is 4.8” and I would guess a slightly chubby 180lbs, Bombur is 4.5, and I would guess a fat 245-260 in the films, although I would put him up to 350 in LOTR books because by them he is immobile... I kid you not Tolkien was the biggest asshole to poor Bombur and milked him as the fat archetype even in that book.
Dwarves, sometimes called the Stout Folk, were a tough, tradition-abiding folk known for their strong martial traditions and beautiful craftsmanship.
Dwarves were a short race, as their name implied, standing from 4'3" – 4'9" on average. What Dwarves lacked in height they made up for in bulk; they were, on average, about as heavy as humans A dwarf could weigh anywhere from about 160 – 220 lbs (73 – 100 kg). Dwarven males were a bit taller and heavier than their female counterparts. Like humans, dwarves had a wide variety of skin, eye, and hair colors, typically pale. Hazel eyes were common throughout the race, with blue eyes more common amongst shield dwarves and brown or green eyes found amongst the gold dwarves.
Dwarves were a long-lived race, and reached physical maturity somewhat later than humans. A dwarf was traditionally considered an adult once he or she reached age fifty. Dwarves aged much like humans but over a longer period of time, remaining vigorous well past 150 years. Most dwarves lived to see their bicentennial and a few lived to be over 400.
Dwarves were unusually tough for humanoids, in more ways than one. Dwarves were resistant to virtually all poisons and it took less effort for a dwarf to get back on its feet than other races. Dwarves also had dense bodies and were difficult to push around as a result, as well as having the capacity to bear loads that other races might find hindering with little ill effect.