Size and weight are big decision factors when you are trying to find the ideal camera for your needs.
In this section, we are going to illustrate the Olympus TG-810 and Nikon D90 side-by-side from the front, back and top in their relative dimensions. Olympus TG-810 has external dimensions of 100 x 65 x 26 mm (3.94 x 2.56 x 1.02″) and weighs 215 g (0.47 lb / 7.58 oz) (including batteries). Nikon D90 has external dimensions of 132 x 103 x 77 mm (5.2 x 4.06 x 3.03″) and weighs 703 g (1.55 lb / 24.80 oz) (including batteries).
Below you can see the front-view size comparison of the Olympus TG-810 and the Nikon D90. Olympus TG-810 is clearly the smaller of the two cameras. Its body is 32mm narrower, 38mm shorter and 51mm thinner than Nikon D90. As you can tell, actually this is not a fair size comparison since Olympus TG-810 has a built-in lens but Nikon D90 doesn't. Once you put a lens on D90, its thickness will increase significantly.
Here is the back view size comparison of the Olympus TG-810 and Nikon D90.
Now lets look at the top view comparison of Olympus TG-810 and Nikon D90.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Olympus TG-810 is significantly lighter (488g ) than the Nikon D90 which may become a big advantage especially on long walking trips.
Again, this comparison may not be very useful in real life as we are comparing the weight of a camera with a built-in lens to the body-only weight of an interchangeable lens camera. Once you put a lens on D90, the total kit will weigh much higher.
Weather Sealing
Thanks to the weather-sealed body of the TG-810, you can use this camera with more confidence under conditions where there is risk of exposure to water and dust compared to the D90.
LCD Screen Size and Features
Olympus TG-810 and Nikon D90's LCD screens have the same diagonal size of 3.00 inches.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.