Planning tool
Seed starting calculator
Choose when you plan to plant outdoors. The calculator counts backward to show when to start one crop or a full list of crops indoors.
Seed-starting calculator
Find when to start seeds indoors
We count backward from the outdoor planting date using university timing guidance.
Need help choosing the outdoor date first? Find your local frost dates or estimate the typical frost-date growing window by ZIP Code, then check the current forecast and crop-specific temperature needs.
How the calculation works
The calculator counts backward by the number of weeks a crop normally grows indoors. For example, tomatoes use 5–6 weeks and peppers use 8–9 weeks in the reviewed university guides.
What the result cannot know
The tool cannot know when your garden is safe for planting. Before entering a date, check your local frost estimate, the crop's temperature needs, the current forecast and the seed packet.