A rough rule of thumb, not a rule
Some sources suggest a young puppy can typically wait roughly as many hours as their age in months, plus about one more — a 3-month-old puppy might manage somewhere around 3–4 hours during the day. Treat this as a planning guide, not a target to push toward.
Day and night are different
Many puppies gain better overnight bladder control around 4–6 months, sometimes sleeping through the night before they can reliably wait that long during an active day. Individual variation is real.
Activity changes the math
A puppy who just woke up, just ate, or just finished an exciting play session usually needs to go sooner than the general guideline suggests, regardless of how long it has technically been.
What to avoid
Keep the response gentle.
Avoid restricting water in the evening as a shortcut — talk to your veterinarian first, since hydration needs vary by age, health, and activity.
Safety boundary
When to get more help.
If your puppy strains, produces very little, or seems to need to go constantly, treat it as a medical question first, not a scheduling one.