SEEDS / SOWING SCHEDULE
Seed Starting Date Calculator
Work backward from your planned outdoor planting date. Enter your seed packet’s indoor lead time to find the right dates to start sowing.
01 / ENTER YOUR DATES
Build your sowing schedule
Choose your outdoor date directly or work from your own local last-frost estimate.
THE METHOD
Work backward from the day you plan to transplant
Choose an outdoor date
Enter the transplant date, or add a signed number of days to your own last-frost estimate to set that target.
Enter the lead-time range
Use the minimum and maximum weeks indoors from your seed packet or crop-specific instructions. A longer lead means an earlier sowing date.
Subtract complete days
Sowing date = target date − (weeks × 7 days). Subtract extra germination days only when they are not already included.
WORKED EXAMPLE
Transplanting May 15 with a 6–8 week indoor lead
May 15 is an arithmetic example, not a recommendation for every U.S. garden. The range gets wider only when the seed packet gives you a range to use.
BEFORE YOU SOW
What this calculator cannot decide for you
Local frost dates describe historical probabilities. A warm week or a calculated date does not make planting conditions certain.
This tool does not choose a seed-specific lead time, soil temperature, hardening-off schedule, or the right transplant day.
If the packet’s indoor lead time includes germination, keep the default option. Otherwise you could move sowing earlier than the instructions intend.
References and Sources
University of Minnesota Extension: Starting seeds indoors. Use crop-specific seed packet timing and allow time to harden off before transplanting. This calculator performs calendar arithmetic only.