How many seeds do I need?
Count the planting spots along each row, multiply by the number of rows and by the seeds you drop in each spot. Then add extra for seeds that fail. A germination rate of 80% means roughly one seed in five will not grow.
Seeds = spots per row × rows × seeds per spot ÷ germination rate
Four rows of beans, each 10 ft long, at 4 in apart: 31 spots per row × 4 rows = 124 spots. At 80% germination, sow 155 seeds.
Planning the rest of the job? Use the Plant population calculator and the Plant spacing calculator too.
Sowing distances
Carrots, radishes, peas
2 in (5 cm)
Beans, beetroot, spinach
4 in (10 cm)
Sweet corn
10 in (25 cm)
Lettuce
12 in (30 cm)
These are sowing distances. Many crops are sown closer and thinned later, so follow the packet if it says otherwise.