Consider the size of the room. Select a lamp that fits the size of the room. A large room needs a larger lamp while a small room needs a smaller lamp for the best look.
Measure the table on which the lamp will rest. Measure its diameter and height. The lamp should be in proportion with the table as well as the room. A large lamp on a tiny table looks out of place and increases the risks of the lamp tipping. A tiny lamp on a large table may get lost visually.
Consider the size of the other furnishings in the room. Choose a table lamp size that works well with the other furnishing sizes. For example, a larger lamp works well with oversized furniture.
Select a lamp shade that is proportionate to the base. Avoid choosing a very large shade for a smaller lamp. It will appear unbalanced and take away from the appearance of the room as a whole.
Test out the lamp size in the room. Place it on the table and stand back to see how it looks in comparison to the other furnishings. If the lamp is near a seating area, sit down and inspect the lamp. The ideal location for the lamp shade is with the bottom of it at eye level when seated.