Signs from below
Is the plant in a pot with a drainage hole? Then take a look under the pot. Are the roots growing out of the drainage hole? This is one of the clearest signs you can find: the plant definitely needs a larger size pot. Carefully loosen the roots from the bottom when repotting so that they are not damaged too much.

Root excess
The roots of a plant can also start to protrude from the top. If this is the case, simply throwing some soil on top will not help. You cannot do this indefinitely. It really is time for a new pot.

Leaf discolouration
Yellow leaves or a large loss of leaves can also be a sign that the plant is ready for repotting. The houseplant can no longer get enough nutrition from the soil to stay strong and healthy. When repotting, make sure you use the right potting soil with a supplement of houseplant nutrition.

Growth stop
Did your houseplant used to grow and flower well and regularly, but now it seems to be doing less well? Then it could be that the plant does not have enough room to continue growing and therefore needs a bigger pot. Please note that plants always have a growth stop in autumn and winter due to the reduction in light.