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Potato Chitting Calculator — Seed Potatoes & Timing
Calculate seed potato quantities, spacing, and chitting times.
Length of each planting row or trench. Allow 60cm between earlies rows, 75cm for maincrop.
How many rows you will plant. One 25kg bag of seed plants roughly 100-125m of earlies row (about 300-420 tubers at 60g each).
Earlies plant 30cm apart and crop fastest; maincrop plant 37cm apart for bigger, later storing tubers.
Optional. UK seed potatoes typically cost £2-£4 per kg; leave at 0 to skip the cost estimate.
Average weight per seed potato (default 0.06 kg / 60g)
Adjust yield for conditions (default 1.0)
How We Calculate This
Tubers per row = (Row length ÷ in-row spacing) + 1, counting a tuber at each end of the row. Total tubers = Tubers per row × Number of rows.
Seed potato weight assumes an average of 60g per tuber (about 16-17 tubers per kg at that size). Yield estimates are based on typical UK conditions and are guides, not guarantees.
Per RHS: first and second earlies 30cm apart in rows 60cm apart; maincrops 37cm apart in rows 75cm apart.
Frequently Asked Questions
Chitting means placing seed potatoes in a cool, light spot (like an egg box on a windowsill) to develop short, sturdy shoots before planting. This gives them a head start.
Start chitting about 4-6 weeks before planting. First earlies plant out in late March, so chit from early-mid February; maincrops plant from mid April, so chit from early-mid March. Seed potatoes are ready once the sprouts reach about 5cm.
At the default average of 60g per tuber, expect roughly 16-17 seed potatoes per kg. Larger seed tubers of about 80-100g give around 10-12 per kg, while small 35mm tubers run nearer 18-20 per kg. UK seed is usually sold in the 35-55mm grade.
Plant seed potatoes 10-15cm deep with shoots facing upward. Earth up (mound soil around stems) as they grow to prevent tubers greening and to boost yield.
Chitting gives the biggest benefit to first and second earlies, where an early start brings the harvest forward. Maincrops grow for longer in the ground, so chitting is optional and often skipped — they still crop well planted straight from the bag in mid April.
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Last updated: February 2026
All calculations are estimates based on standard gardening guidelines. Results may vary with soil conditions, climate, and plant varieties.