Indoor Seed Starting Date Calculator
Work backwards from an intended outdoor planting date to plan a crop-specific indoor seed-sowing window.
How to use this tool
Crop; intended plant-out date; seed packet indoor lead-time when available. Check the units and use measurements from the growing space or instructions for your actual crop or product.
What the result means
Estimated indoor sowing range and a practical hardening-off reminder. The result follows the inputs you provide; it does not replace inspection of your plants or the relevant product label.
Worked example
For a 1 June planting-out date with an indoor lead time of 42–56 days, sowing falls between 6 and 20 April. For a crop dated 1 June with 60–80 days to maturity, the estimated window is 31 July–20 August. The entered range must come from your chosen variety’s instructions.
Assumptions and limitations
Depends on germination temperatures, cultivar and seed-packet instructions. This tool uses explicit arithmetic and your inputs; it does not connect to weather, location, product or soil databases.
Start window = intended planting-out date minus lead-time range.
A useful next read
