Before determining what is the size of carpet you need, it is important to understand that the main function of a rug is harmonising all the elements in a room. So to create balance, you can wonder first about the style you are trying to pursue and where the furniture is positioned.
Try layering rugs, it always looks better when you use different sizes. Find one large one then add smaller ones on top to serve as accents.
Experiment with angles by trying out different ways to style your rugs. If you're layering with different shapes, have the first one laid down straight, then move the smaller ones around until you find a position that works best.
When it comes to color, you want your rugs to be tonal or complementary. Find different shades of the same color and layer them based on your preferred look.
Kitchen & Dining Room
Picking a rug here will depend directly on the size of the dining table. The key rule to keep in mind is that you need enough space beyond the edge of the tabletop to drag the chairs in and out. So only make sure there is around 45-60 cm of a rug edge behind the back legs of the dining chairs so they won't touch the floor when pulled out.

Dining Room I
Rugs of around 275x365 cm can be a good fit for 8-chaired dining tables.

Runner for the Kitchen
To place a rug in the kitchen, you can determine the size yourself by calculating the area left upon leaving 45-60 cm of space along the sides.

Dining Room II
Regardless of whether the dining table is circular or square, the standard prices to consider are ⌀ 160, ⌀213, ⌀244, ⌀250, ⌀305, ⌀376 and oversized.

Dining Room III
Rugs of around 240x300 cm can be a good fit for 6-chaired dining tables.
Living Room
Placing almost any size of an area rug in a living room is possible. To give you an idea, for a small area, the best-sized rug would be ca. 120x180 cm. For a medium-sized living room, 180x275 cm can be optimal. And for a large spot, a 240x305 cm would be perfect for gathering together the whole furniture layout.

Living Room I
If you have an L-Sofa, big rugs of dimensions close to 305x420cm can add a holistic feeling to the atmosphere.

Living Room II
Leaving 45 cm of space between the rug and the furniture and placing a carpet of 180x275 cm, for example, can stimulate the feeling of wideness.

Living Room III
L-Sofas can be a challenge that can be easily overcome by placing a small or medium rug in the middle. Starting from sizes 120x180 cm.

Living Room IV
To suit oversized spaces, we recommend sizes between 240x305cm. The room will look breezy and cosy.
Bedroom
The ideal choice lies in the dimensions of your room, the size of the bed and how much space you have in front of it. You can furnish small bedrooms with carpets either 90x150 cm or 120x180 cm. Large areas would need carpets between 150x240 cm and 180x275 cm. You can also play a bit by placing runners on the sides.

Bedroom I
Placing runners by any border of the bed could bring a different accentuation around its periphery.

Bedroom II
To allow a bare floor circulation area at the foot of the bed, place a rug under it. Sizes can vary from 180x275, 240x305 or 275x36 cm.

Bedroom III
When the space in front of the bed has been designed as a sitting area or to place a bench, try adding rather a rug 150x240 cm or a runner.

Bedroom IV
Oversized rugs fit perfectly on large surfaces. Better is to furnish them in a vertical orientation or best to choose a nice square piece.