Use the balcony plant calculator below to find out how many pots fit your space, whether your slab can handle the load, and which plants work for your orientation and season — all in an interactive 3D view. For the full picture, see our balcony gardening hub.
Urban Architect
Typical: Concrete slab ~450 · Steel frame ~250 · Old wood ~150
Why Use a Balcony Plant Calculator?
Most balcony gardeners eyeball it — and then wonder why their pots tip over in July or why the slab creaks under a row of concrete planters. A calculator removes the guesswork with actual numbers:
- Plant Slots: Exact pot count for your dimensions and plant type — from 7 trees to 86 herb pots on a 3.6 m² balcony.
- Structural Load: Total weight in kg and kg/m² — flagged green, amber, or red against your building’s limit.
- Seasonal Fit: The planner dims plants that are wrong for the current season and adds a tailored shopping list for Spring, Summer, Autumn, or Winter.
- Shareable Plan: Copy a URL with all your settings to share with a partner or a nursery, or download a PNG layout to bring in-store.
Understanding Balcony Load Limits
Modern concrete balconies typically handle 200–450 kg per square metre. Steel-frame balconies average 250 kg/m²; older wood-frame structures can be as low as 150 kg/m². Three things city gardeners consistently underestimate:
- Wet soil doubles pot weight. A 5-litre plastic pot weighs ~0.5 kg dry. After watering: closer to 6 kg. The calculator adds 5 kg per pot automatically for wet-soil weight.
- Point loads beat distributed loads. One 25 kg concrete planter on four small feet concentrates all weight on a 200 cm² footprint — far worse than spreading the same mass across many small plastic pots.
- Plastic saves up to 60% payload. Switching from terra cotta (9 kg/pot) to plastic (1.5 kg/pot) on a fully planted 4 m² balcony cuts dead load by roughly 90 kg. See how the balcony weight limit guide explains the maths.
How to Use the 3D Balcony Planner
- Enter dimensions. Width and depth in metres. The 3D floor scales in real time.
- Pick orientation. North, South, East, or West. The planner flags incompatible plant choices — tomatoes on a north-facing balcony get an automatic warning.
- Set the season. Spring, Summer, Autumn, or Winter. Unsuitable plants dim out and the shopping list adds seasonal extras — frost fleece in Autumn, drip timers in Summer.
- Choose plant type and pot material. Density and weight change instantly. Concrete pots push the load gauge toward amber fast.
- Check the load gauge. Green = safe. Amber = caution (above 70% of limit). Red = overload risk — reduce pot count or switch to lighter containers.
- Download or share. PNG export captures the 2D top-down plan. The Share button copies a URL with every setting pre-filled — useful for discussing with a partner or bringing to a garden centre.
Balcony Gardening Tips by Orientation
The single biggest factor in what you can grow is which direction your balcony faces. Here’s the short version — and the planner enforces this automatically:
- South-facing: 6–8 hours direct sun. Best for tomatoes, petunias, and herbs. In peak summer, add a 30–40% shade cloth at midday. Consider wind-resistant varieties if you are above the 5th floor.
- North-facing: Shade most of the day. Stick to mint, parsley, chives, and ferns. Avoid tomatoes — they won’t ripen without 6+ hours of sun. See our shade-tolerant vegetable guide for options.
- East-facing: Morning sun, afternoon shade — ideal for herbs and leafy greens that bolt in afternoon heat. Good for a self-watering setup since soil dries more slowly.
- West-facing: Afternoon sun from 13:00 onward. Good for most flowers. Avoid large trees — they grow asymmetrically toward the sun and can become unbalanced in containers.
After the Calculator: Your Next Steps
Got your plant count and load number? Here is what to do with it:
| Your Result | What It Means | Next Step |
|---|---|---|
| 🟢 Green load gauge | Under 70% of your slab limit — safe to plant | Set up your drainage system before filling pots |
| 🟡 Amber load gauge | 70–100% of limit — reduce pot count or switch materials | Switch pot material to plastic or fabric grow bags; re-run the calculator |
| 🔴 Red load gauge | Overload risk — do not proceed | Read the full balcony weight limits guide and confirm your slab rating with building management |
| North-facing balcony | Limited to shade-tolerant plants naturally | Add LED grow lights to expand what you can grow |
| Smart irrigation flagged | High plant density needs automation | See our smart self-watering herb gardens guide |
Frequently Asked Questions
How many plants can fit on a 3m × 1.2m balcony?
A 3 × 1.2 m balcony (3.6 m²) fits roughly 86 herb pots in small plastic containers, 43 tomato plants, or just 7 small trees — depending on density settings. Set your exact dimensions in the calculator above for a precise count.
What is a safe weight limit for an apartment balcony?
Most modern concrete balconies handle 200–450 kg per square metre. Steel-frame balconies average around 250 kg/m², and older wooden structures can be as low as 150 kg/m². The calculator flags your total load against the limit you enter — ask your building manager if unsure.
Can I use this balcony planner on a phone?
Yes. The planner collapses to a single-column layout on screens under 1100 px. Drag-to-rotate works with touch gestures. The 2D Plan toggle is easier to use on small screens than the 3D view.
What plant density is good for a beginner?
Start with 12–16 pots per m² in medium plastic containers. That keeps your total load under 120 kg/m², leaves walking space, and makes watering manageable. The Herbs setting in the calculator uses 36 per m² — that’s a productive but high-effort setup that needs watering every 1–2 days in summer.
Does balcony orientation affect what I can grow?
Yes — it’s the single biggest factor. South-facing balconies get 6–8 hours of direct sun, suitable for tomatoes and most flowers. North-facing spots suit shade-tolerant herbs like mint and parsley. The planner displays a warning automatically if you pick an incompatible combination.