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-870 and Nikon D5000 side-by-side from the front, back and top in their relative dimensions. Olympus TG-870 has external dimensions of 113 x 64 x 28 mm (4.45 x 2.52 x 1.1″) and weighs 221 g (0.49 lb / 7.80 oz) (including batteries). Nikon D5000 has external dimensions of 127 x 104 x 80 mm (5 x 4.09 x 3.15″) and weighs 590 g (1.30 lb / 20.81 oz) (including batteries).
Below you can see the front-view size comparison of the Olympus TG-870 and the Nikon D5000. Olympus TG-870 is clearly the smaller of the two cameras. Its body is 14mm narrower, 40mm shorter and 52mm thinner than Nikon D5000. As you can tell, actually this is not a fair size comparison since Olympus TG-870 has a built-in lens but Nikon D5000 doesn't. Once you put a lens on D5000, its thickness will increase significantly.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Olympus TG-870 is significantly lighter (369g ) than the Nikon D5000 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 D5000, the total kit will weigh much higher.
Weather Sealing
Thanks to the weather-sealed body of the TG-870, you can use this camera with more confidence under conditions where there is risk of exposure to water and dust compared to the D5000.
LCD Screen Size and Features
Olympus TG-870's 3.00" LCD screen is slightly larger than Nikon D5000's 2.7 screen.