Planting Date Calculator
Find indoor start and transplant dates from USDA zone and last frost date.
Covers tomatoes, peppers, cucumbers, and 30+ crops with days-to-maturity guidance.
Planting Schedule
Planting date calculation determines the optimal time to start seeds indoors or transplant seedlings outdoors based on your last frost date and each crop’s cold tolerance.
The Formula:
Outdoor planting date = Last Frost Date + (Cold hardiness offset in days)
Indoor start date = Outdoor planting date − (Weeks to transplant size × 7)
Cold Hardiness Categories:
| Category | Plant Examples | Offset from Last Frost |
|---|---|---|
| Hardy (survive frost) | Kale, broccoli, lettuce, peas | −4 to −6 weeks (plant early) |
| Semi-hardy | Chard, beets, carrots | −2 to −4 weeks |
| Tender (frost kills) | Tomatoes, peppers, basil | 0 to +1 week (after last frost) |
| Very tender | Cucumber, squash, melons | +1 to +2 weeks |
Indoor Start Lead Times:
| Crop | Weeks Before Transplant Date |
|---|---|
| Tomatoes | 6–8 weeks |
| Peppers | 8–10 weeks |
| Broccoli / Cabbage | 4–6 weeks |
| Lettuce | 3–4 weeks |
| Basil | 4–6 weeks |
Worked Example:
Last frost date: April 20. Planning to grow tomatoes:
- Outdoor transplant: April 20 + 0 days = April 20 (or up to May 1 to be safe)
- Indoor start: April 20 − (8 weeks × 7) = April 20 − 56 days = February 23
Practical Tips:
- Find your last frost date using USDA Hardiness Zone maps or your local agricultural extension office
- Late frosts happen — keep row cover fabric ready until nights consistently stay above 4 °C (40 °F)
- Soil temperature matters as much as air temperature: most seeds germinate best at 18–24 °C (65–75 °F) soil temp
- Harden off transplants over 7–10 days before moving outdoors permanently