Most children are ready for potty training between 18 months and 3 years. There's no "right" age - starting before your child is ready doesn't speed things up and often makes the process longer and more stressful for everyone.
Signs of readiness
Your child is likely ready when they: know when they have a wet or dirty nappy (they might tell you, or go quiet and hide); have regular, predictable bowel movements; can stay dry for at least an hour or two; show interest in the toilet or potty; can follow simple instructions; can pull their trousers up and down; and seem uncomfortable in a wet nappy.
You don't need ALL of these - but if most are present, it's worth trying.
How to start
Let your child choose a potty and put it somewhere accessible. Switch to easy-on, easy-off clothing - loose trousers or skirts, no dungarees or complicated buttons. Start with nappy-free time at home, sitting them on the potty at regular intervals - after meals, after naps, before bath.
Praise success warmly but calmly - "well done, you did a wee on the potty!" is better than a massive celebration that creates pressure. Accidents are not failures - clean up without fuss. "Oops, that's OK. Let's try the potty next time."
Most children get daytime dryness within 3-6 months of starting. If after two weeks there's been no progress at all, it's fine to stop and try again in a month.
Potty training regression
Going backwards after initial success is extremely common and is usually triggered by a big change - new sibling, house move, starting nursery, illness, or general stress. Go back to basics without pressure. Don't put them back in nappies unless they ask - this can feel like a punishment. It almost always resolves within a few weeks.
Night-time dryness
Daytime and night-time dryness are separate developmental milestones. Night-time dryness depends on the body producing enough antidiuretic hormone (ADH) during sleep, which is not something children can control or be trained to do. Most children are dry at night by age 5, but bedwetting up to age 7 is still within the normal range.