How Much to Grow Calculator

Free How Much to Grow Calculator — Find Out Exactly What to Plant for Your Household

One of the most common frustrations on the allotment is misjudging how much to grow. Plant too little and you're back buying from the supermarket by July. Plant too much and you're drowning in courgettes with no idea what to do with them. Our free How Much to Grow Calculator solves both problems — just tell us your household size, how often you want to eat each vegetable, and we'll work out exactly how many plants, how many row metres, and roughly how many seeds you need to buy.

Scaled from a single raised bed right up to a full allotment plot. Works for every vegetable we sell.

How the Calculator Works

The tool is built around real portion sizes, realistic crop yields, and a standard 20-week UK growing season. Tell us three things and we do the rest:

• Your household — how many adults and children you're growing for, with children counted at 65% of an adult portion
• Your ambition level — whether you want to supplement your shopping, become fully self-sufficient in that crop, or grow a surplus to preserve, freeze or share
• How often you want to eat each veg — never, fortnightly, weekly, or twice a week. Only crops you want to eat appear in your results

From those inputs the calculator works out your weekly and seasonal kilogram requirement for each crop, divides that by the realistic yield per plant or per row metre, and gives you a complete growing plan.

What Your Results Include

• Total crops in your plan — a count of everything you've chosen to grow
• Total plants needed — across all plant-based crops in your selection
• Total row metres — the combined row length needed for direct-sown crops
• Approximate bed space — an estimated square meterage so you can check it fits your plot
• A crop-by-crop breakdown — showing plants or row metres, frequency, and approximate seed quantities for every crop in your plan
• Personalised growing tip — flagging anything in your plan that needs attention, such as space-hungry crops or a plan that exceeds a typical plot size

How Yields and Portions Are Calculated

Every crop in the calculator uses realistic UK allotment yields — not the optimistic figures you sometimes see on seed packets. A courgette plant realistically produces around 6kg over a season. A metre of runner beans gives around 1.2kg. A potato plant yields roughly 700g. Portion sizes are based on standard UK serving weights, so a carrot portion is 150g, a tomato portion is 150g, and a lettuce counts as 80g. These figures are designed to give you a practical, achievable plan rather than an aspirational one.

Tips for Getting the Most From Your Plan

• Don't grow everything at once — the calculator gives you totals for the whole season. For crops like lettuce, radish and spinach, split your row metres across several sowings rather than planting everything in one go. This spreads your harvest and avoids a glut
• Add 20% extra seeds — the seed quantities shown already include a 20% buffer for germination failures, slug damage and thinning. Don't cut this down if you can help it
• Check your bed space figure — if your approximate bed space is coming out above 50m² you may need to prioritise. Think about which crops give you the best return for their space, and which you can supplement from the shops if needed
• Space-hungry crops need planning — courgettes, pumpkins and squash need 90cm to 120cm between plants. If these are in your plan, map out where they'll go before you commit to buying seeds
• Start with what you actually eat — it sounds obvious, but the calculator works best when you're honest about frequency. If your family only eats broccoli occasionally, set it to fortnightly rather than weekly

Covers All 36 Vegetable Categories We Sell

Every crop in the calculator links directly to the relevant seed category on the Growseed website, so once you've built your plan you can go straight to browsing the right varieties. All our seeds are hand-picked, UK-tested, and chosen for flavour, reliability and performance in British growing conditions.