Greenhouse Size Calculator UK — Find Your NORDIC Match
Waldenhaus · Free tools · 01 — Size
Find your NORDIC size.
Tell us about your household and what you want to grow — we'll match you to the right size from the NORDIC range, with the floor area maths and realistic yield estimates.
Your NORDIC match
NORDIC-M
8 × 10 ft · 2.4 × 3.0 m · 7.8 m² floor area · from £1,199
Realistic annual yield estimate
Estimates are based on typical UK garden growing, with NORDIC's 4 mm twin-wall CrystalLight polycarbonate, screw-fixed glazing, and active venting. Actual yields vary with season, sun exposure, and growing technique.
— How it's calculated
How this calculator works
The greenhouse size calculator works in three steps. First, it allocates floor area per crop based on typical UK growing densities: tomatoes need roughly 0.8 m² per indeterminate plant (with vertical training), cucumbers 0.5 m², peppers 0.4 m², leafy greens 0.2 m² per portion, herbs 0.1 m² per plant, and a starter seedling station around 0.5 m². Second, it scales the totals by household size — a 3–4 person family eats roughly 1.5× what a 1–2 person household eats; 5+ people, 2.0×. Third, if you grow year-round (September–April included), it adds about 30% extra space for staggered sowing and overwintering crops.
The result maps to one of the five NORDIC sizes — from NORDIC-S at 5.2 m² to NORDIC-XXL at 15.6 m². All five share the same 45×45 mm Swedish pine from sustainably-managed forests cross-section, the same 1.2 mm galvanised steel joints, and the same screw-fixed 4 mm CrystalLight polycarbonate panels. The only thing that changes between sizes is footprint length — so you don't trade engineering quality for size.
What size do most UK households actually need?
The most common honest answer for a UK household of three or four people growing the typical mix — tomatoes, cucumbers, peppers, some leafy greens and herbs, with seedlings in spring — is the NORDIC-L (8×13 ft, 10.4 m²). That's the sweet spot: enough room for two ground beds, generous walkway, and overhead space for indeterminate tomato varieties without crowding.
For a 1–2 person household focused on a few tomato plants plus salad leaves and herbs, the NORDIC-S (8×6 ft, 5.2 m²) is enough. For 5+ people or a serious year-round grower with mixed crops including overwintering brassicas and an extensive seedling operation, you'll want the NORDIC-XL (8×16 ft) or NORDIC-XXL (8×20 ft).
The mistake most UK growers make on size
The single most common regret in greenhouse buying is "I should have gone one size larger". Two reasons. First, your growing ambition expands once you have the structure — what starts as "just tomatoes" becomes tomatoes, cucumbers, peppers, herbs, seedling propagation, and overwintering tender crops within two seasons. Second, the per-square-metre cost drops as size goes up: NORDIC-S works out at £192/m², NORDIC-XXL at £99/m² — less than half the unit cost.
That said, going too large for your plot creates its own problems: more glazing to clean, more frame to maintain, and risk of falling outside UK Permitted Development limits if the structure exceeds 2.5 m eaves height or covers more than 50% of the garden area. The calculator is conservative — it aims for "comfortable fit with room for staging" rather than maximum compression.
Floor area is only half the story
A 7.8 m² greenhouse can grow dramatically different yields depending on layout, height, glazing quality, and venting. NORDIC's ridge design accommodates 2.1–2.4 m tall indeterminate tomato varieties without crowding; the 4 mm CrystalLight twin-wall panels transmit ~85% light while insulating roughly 33% better than single horticultural glass; and the screw-fixed glazing handles British storm conditions where spring W-clip glazing on cheap kits typically fails by year two. Read more on the wind-resistance engineering.
— Questions, answered
Frequently asked questions
What size greenhouse do I need for tomatoes only?
For tomatoes alone, a 2m or 3m greenhouse is sufficient — you can typically fit 12–18 tomato plants depending on variety. However, most growers expand into cucumbers, peppers, and herbs alongside tomatoes within two seasons, in which case the 4m (NORDIC-L) becomes the more practical baseline.
How does year-round growing change the size requirement?
Year-round growing in the UK means September–April includes overwintering crops, propagation for spring, and continued leafy green production. This adds about 30% extra floor area requirement compared to seasonal Mar–Oct growing — you need space for staggered sowing trays, overwintering brassicas, and protected salad crops simultaneously.
Can I grow in a smaller greenhouse and still get good yields?
Yes, but only with high-density vertical growing techniques. NORDIC-S (5.2 m²) can yield 25–35 kg of tomatoes per season with cordon training and grow bags. The trade-off is constant management: you can't leave it alone for a week. Larger sizes (NORDIC-L and up) are forgiving — you can take holiday in July without losing the crop to neglect.
Do I need planning permission for the size the calculator recommends?
In most cases in England, no — a greenhouse under 2.5 m eaves height covering less than 50% of the garden is permitted development. All five NORDIC sizes fall within these thresholds for typical UK garden sizes. Rules differ in Scotland, Wales, and Northern Ireland, and conservation areas have stricter limits. See our UK Permitted Development guide for specifics.
What about anchoring — does size affect the base I need?
All NORDIC sizes use the same Heavy-duty Ground Anchors that hammer straight into the soil — no concrete pad required. Larger greenhouses (NORDIC-L and up) come with more anchor points to handle higher wind loads, but the base preparation is the same: level ground, drainage consideration, capillary break. See our base preparation guide.
How accurate are the yield estimates?
The estimates reflect realistic UK home-growing yields with standard varieties, active venting, and reasonable care. A skilled grower with optimised varieties and intensive management can exceed these numbers by 30–50%; a beginner in the first season may achieve 60–70% of the estimate. The supermarket-equivalent value uses £4/kg as an average across mixed crops at typical UK retail.
Can I upgrade later if I outgrow my greenhouse?
Yes — there's no penalty for sizing up later, but the per-m² cost is lower when you buy a single larger greenhouse rather than two smaller ones over time. The NORDIC range uses the same engineering and components across all sizes, so a larger greenhouse is a proportionally similar investment per m² of growing space, just with more frame and more glazing.
— Keep planning
Related reading
- What size greenhouse do I need? — practical UK sizing guide
- 9-step buyer's checklist — what to confirm before clicking buy
- Total cost UK 2026 — kit + base + delivery + 10-year maintenance
- UK Permitted Development rules — do you need planning permission?
- Where to place a greenhouse in your UK garden — sun, shelter, access
- Waldenhaus wooden greenhouses — main hub