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Frost Date Planting Window Calculator

Work out frost date planting window instantly with clear inputs, formula shown and shareable results.

About Frost Date Planting Window Calculator

The frost free window is the number of days between the last spring and first autumn frost, and the latest sowing date counts the crop's maturity period back from the autumn frost. Knowing the spare days is what tells you whether a second sowing is realistic or whether the season only supports one crop of that variety.

Formulas

Growing window

window = days between last spring frost and first autumn frost

Latest sowing

latest sow date = first autumn frost - days to maturity

Worked example

With the default values below, Frost Date Planting Window Calculator returns Frost free growing window of 155. Change any input above and every figure here is recalculated in your browser.

Inputs used

Last spring frost
2026-05-10
First autumn frost
2026-10-12
Days to maturity for the cropminimum 1
75

Results

Frost free growing window
155 days
Latest sensible sowing date
2026-07-29
Successive crops the window allows
2
Spare days beyond one crop
80

Step by step

  1. 1Values used
  2. 2Growing window
  3. 3Latest sowing
  4. 4Frost free growing window= 155 days
  5. 5Latest sensible sowing date= 2026-07-29
  6. 6Successive crops the window allows= 2
  7. 7Spare days beyond one crop= 80

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Frost Date Planting Window figure worked out?

window = days between last spring frost and first autumn frost. The frost free window is the number of days between the last spring and first autumn frost, and the latest sowing date counts the crop's maturity period back from the autumn frost.

Why does this matter?

Knowing the spare days is what tells you whether a second sowing is realistic or whether the season only supports one crop of that variety.

What do I need to enter?

Enter last spring frost, first autumn frost, days to maturity for the crop. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.

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