Size and weight is a big decision factor when you are trying to find the ideal camera for your needs.
In this section, We are going to illustrate Nikon D3400 and Sigma DP2 Quattro side-by-side from the front, back and top in their relative dimensions. Nikon D3400 has external dimensions of 124 x 98 x 76 mm (4.88 x 3.86 x 2.99″) and weighs 395 g (0.87 lb / 13.93 oz) (including batteries). Sigma DP2 Quattro has external dimensions of 161 x 67 x 82 mm (6.34 x 2.64 x 3.23″) and weighs 395 g (0.87 lb / 13.93 oz) (including batteries).
Below you can see the front view size comparison of Nikon D3400 and Sigma DP2 Quattro. Nikon D3400 is 37mm narrower and 6mm thinner than Sigma DP2 Quattro but it is also 31mm taller. As you can tell, actually this is not a fair size comparison since Sigma DP2 Quattro has a built-in lens but Nikon D3400 doesn't. Once you put a lens on D3400, its thickness will increase significantly.
Here is the back view size comparison of Nikon D3400 and Sigma DP2 Quattro.
Now lets look at the top view comparison of Nikon D3400 and Sigma DP2 Quattro.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Nikon D3400 and Sigma DP2 Quattro have exactly the same weight of 395g.
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 D3400, the total kit will weigh much higher.
Unfortunately neither Nikon D3400 nor Sigma DP2 Quattro provides any type of weather sealing in their body, so you have to give extra care especially when you are shooting outdoors. If weather sealing is a must-have feature for you, check these sections: Top DSLR Cameras with Weather Sealing Top Compact Cameras with Weather Sealing
LCD Screen Size and Features
Nikon D3400 and Sigma DP2 Quattro's LCD screens has the same diagonal size of 3.00".
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.