Direct answer: The best timing depends on your dog’s breed size, health, and your goals. In general:

• Small and medium breeds: spay around 5–9 months (often 5–6 months for very small dogs; 6–9 months is common for medium).
• Large and giant breeds: many veterinarians suggest waiting longer, typically around 12–18 months, to support longer bone and joint development.
• Some homes with giant breeds or dogs at higher risk for certain conditions may choose 12–15 months, while others may opt for 15–18 months depending on the dog’s growth and development.

Key factors to discuss with your veterinarian:

• Growth and orthopedic health: delaying spay in large/giant breeds can support musculoskeletal maturation.
• Cancer and urinary incontinence risks: timing can influence breed-specific risks; some breeds may benefit from earlier spaying for cancer risk reduction, others may have elevated joint or other risks if altered too early.
• Heat cycles and behavior: spaying before the first heat prevents pregnancy and can impact behaviors and certain risks; some owners choose timing to avoid heat cycles.

What to do next:

• Check your dog’s current age, expected adult size, and any breed-specific guidance from your vet. If unsure, schedule a consult to tailor the timing to your dog's individual health, breed, and lifestyle.

If you'd like, share your dog’s breed (or approximate size), current age, and any health concerns, and a more precise range can be suggested based on common veterinary guidelines.