Advanced options
Yields assume decent care: cordons trained to one stem with side shoots pinched, watered CONSISTENTLY (irregular watering = split fruit and blossom end rot), weekly tomato feed from first truss. Sow March indoors, plant out after frost, expect fruit July-October. The honest accounting: seeds and compost cost less than the harvest's worth by year one; the greenhouse takes longer to pay off.
What The Tomato Yield Calculator Works Out
- Expected harvest: plants x a typical yield per plant: about 3.5kg for a cordon under glass, 2.5kg outdoors in a decent summer, 2kg for bush and tumbling types, 1.5kg for cherries in pots. Four greenhouse cordons is 14kg, converted to 250g supermarket punnets.
- Shop value: kilograms x the shop price per kilo you enter (GBP 3/kg is a middling supermarket figure; cherry and vine tomatoes are dearer). Four plants return GBP 40-plus of fruit from a couple of pounds of seed and a bag of compost, the veg garden's most reliable profit line.
- Growing needs: at least 10 litres of growbag or pot per plant, canes, and the daily summer watering. The famous disorders are irrigation biography: split fruit follows feast-after-famine watering, blossom end rot is drought stress, not soil deficiency.
- Custom yield and season (advanced): type a yield from your own records or the seed packet, and adjust for the season: excellent care in a warm summer adds about 25%; patchy watering loses 25%; a wet, blighty summer can halve an outdoor crop.
- Punnet size (advanced): compare against 250g, 300g, 400g or 500g packs so the punnet count matches what you actually buy.
- Costs this season (advanced): plants x the cost per plant (or your share of a seed packet) plus compost, feed and canes, with a cost per kilo grown. A packet of seed is GBP 2 to GBP 4 for ten or more plants, a growbag GBP 3 to GBP 5.
- Net saving (advanced): shop value less this season's costs, with the return multiple. If the costs exceed the fruit's value you are growing for flavour, which is a perfectly good reason.
- Per week in season (advanced): the harvest spread over the season length (14 weeks from July to October by default) in kilos, punnets and grams per person per day, which is where the August glut and the chutney tradition come from.
- Set-up payback (advanced): how many seasons a one-off cost such as a greenhouse takes to repay from tomato savings alone. It amortises faster across the spring seedling factory and the autumn extension it gives everything else; the growbag on a sunny patio delivers the tomato experience for a tenner.
- Type comparison table (advanced): the same number of plants as greenhouse cordons, outdoor cordons, bush and pot cherries, with punnets, value and net. Heavy-cropping F1 varieties out-yield the heritage beauties that repay in flavour what they withhold in weight.