They may look similar in the tin, but interior and exterior paints are engineered for very different jobs.
Exterior paint
Formulated to handle direct sun, heavy rain and temperature swings. It resists fading, repels water and often includes anti-fungal properties for shaded, damp-prone walls.
Interior paint
Built for comfort and looks indoors: low odour, low-VOC options, a smooth finish and washability so marks wipe off easily.
Why the difference matters
Interior paint on an exterior wall fades and peels quickly. Exterior paint indoors can be needlessly high in odour. Matching the right system to the surface is what makes a finish last.