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A raised bed planner that fits the bed you actually built
Most planners assume a tidy 4×8 rectangle. Real gardens have a 3×11 strip down the fence, two half-barrels and a bed with a wonky corner. Niwa takes the dimensions you give it, grids them, and plans every bed you own in one app.
A raised bed planner should do four things you cannot easily do on paper: size a grid to arbitrary dimensions, hold more than one bed at a time, tell you how much soil the bed will swallow, and date each crop to your own frost rather than a zone average. Niwa does all four on iPhone, offline, without an account.
Start with the three numbers that decide everything
Before any app is useful, you need the bed's inside width, length and depth. Inside, because the timber grows nothing — a bed built from 8-foot boards around 2-inch stock is 7 feet 8 inches of soil, not 8.
| Bed size | Square feet | Soil at 12" deep | Suits |
|---|---|---|---|
| 2 × 4 ft | 8 | 8 cu ft · 0.30 cu yd | Herbs, salad, a first bed |
| 3 × 6 ft | 18 | 18 cu ft · 0.67 cu yd | Balcony or courtyard |
| 4 × 4 ft | 16 | 16 cu ft · 0.59 cu yd | The classic square foot bed |
| 4 × 8 ft | 32 | 32 cu ft · 1.19 cu yd | Most common home bed |
| 4 × 12 ft | 48 | 48 cu ft · 1.78 cu yd | Serious vegetable production |
| 2 × 8 ft (against a wall) | 16 | 16 cu ft · 0.59 cu yd | Reach from one side only |
Depth matters more than people expect. Ten to twelve inches covers lettuce, brassicas, tomatoes and beans comfortably. Carrots, parsnips and daikon want eighteen. If your bed sits on concrete rather than soil, add four inches to whatever you were going to build, because roots cannot escape downwards. Run your own dimensions through the soil calculator →
How Niwa plans a raised bed
Any dimensions, gridded to the foot
Enter width and length and the bed appears with a one-foot grid drawn over it. Partial squares along an edge are kept rather than rounded away — a 3.5-foot width gives you a half-row that is perfectly good for chives, lettuce or a row of radishes.
Several beds, kept apart
Beds are grouped into gardens. Keep “Back garden” with three beds and “Allotment” with six as separate plans and switch between them, rather than trying to hold nine beds in one drawing. The bed header tracks how full each one is — 4' × 8' · 24/32 planted — so you can see at a glance where there is still room.
Spacing handled per crop
Drop a crop into a square and Niwa fills it at the right density and labels the count. Sixteen carrots, nine beets, four lettuce, one broccoli. No chart to consult. More on the square foot grid →
Companion dots between neighbouring squares
Green where two neighbours help each other, red where they should be separated. In a raised bed this matters more than in a row garden, because everything is within a foot of everything else. How companion mode works →
A calendar per bed
Once the bed is planted out on screen, every crop in it gets sowing, transplant and harvest windows on a month-by-month timeline, counted from your own last and first frost. See the planting calendar →
The order to plan a raised bed in
Fix the bed's orientation
Note which edge faces north. Everything about height and shading follows from it, and it is the one thing you cannot change later without moving the bed.
Reserve the north strip for tall crops
Tomatoes, trellised cucumbers, climbing beans, sweetcorn. Place these first. A trellis on the north edge is free vertical space; on the south edge it is a wall of shade.
Place perennials and long-season crops next
Anything that occupies its square from March to October — kale, chard, purple sprouting broccoli, strawberries. These squares are unavailable for succession, so decide them early.
Fill the rest with fast crops you can re-sow
Radish at 25 days, lettuce at 45, spinach at 40. These squares turn over two or three times a season, which is where a raised bed's real yield comes from.
Sweep for red dots, then check the calendar
Fix any companion clashes, then open the calendar tab and buy seed from that list rather than from the rack.
The mistake that costs the most space: one courgette plant needs about nine square feet once it is grown. Two of them will eat a 4×4 bed entirely. Plan for the size the plant reaches in August, not the size of the seedling in May.
Filling the bed: what to put in it
Do not use garden soil on its own — it compacts in a raised bed and drains badly. Mel's Mix, the standard square foot recipe, is one third compost, one third peat moss or coconut coir, one third coarse vermiculite by volume. For a 4×8 bed at 12 inches that is roughly 10.7 cubic feet of each.
Bags are sold in cubic feet in the US and litres in the UK and EU. One cubic foot is 28.3 litres. A 32-cubic-foot bed therefore needs about 906 litres — which is why bulk delivery gets cheaper than bags somewhere around the second bed. The calculator does this conversion and the three-way split →
Crop rotation across several beds
With more than one bed, rotation becomes easy: move each plant family on by one bed each year. The four groups worth tracking are nightshades (tomato, pepper, potato, eggplant), brassicas (cabbage, broccoli, kale, radish), legumes (peas, beans) and roots (carrot, beet, parsnip). Legumes fix nitrogen, so following them with brassicas — which are hungry — is the one pairing worth deliberately arranging.
Keeping each bed as its own plan in Niwa makes year-on-year rotation legible: you can see what was in bed two last season rather than trying to remember it.
Related reading
- Square foot gardening: the complete method — spacing chart, Mel's Mix, succession planting
- How to plan a vegetable garden — site, sun and sizing before you build
- Companion planting guide — the pairings behind the dots
Lay out every bed you own in one evening.
Any size, any number of beds, dated to your own frost. Free on iPhone.
Questions gardeners ask
What size should a raised bed be?
Four feet wide is the standard because it lets you reach the centre from both sides without stepping on the soil. Against a wall or fence, drop to two feet. Length is unconstrained — 4x8 is the most common because timber and liners come in 8-foot lengths. Depth of 10 to 12 inches suits almost everything; go to 18 inches for carrots, parsnips and other long roots.
Work out soil volume for your sizeHow many plants fit in a 4x8 raised bed?
A 4x8 bed is 32 square feet, so 32 square-foot cells. Planted at standard square foot densities that is typically 150 to 250 individual plants, depending on the mix — a square of carrots alone holds 16, while a vining tomato takes up four squares on its own.
Count plants for your bedIs Niwa free to use?
Yes. Niwa is free to download from the App Store, and the core planner — the garden grid, the plant library and the planting calendar — works without paying. Optional in-app purchases unlock additional features.
See it on the App StoreHow many plants fit in one square foot?
It depends on the crop's spacing requirement. A plant needing 3 inches fits 16 per square foot, 4 inches fits 9, 6 inches fits 4, and 12 inches fits 1. Large plants such as vining tomatoes or zucchini need more than one square each. Niwa works this out for you and prints the count straight onto the grid cell.
Plants per square foot calculatorCan Niwa plan a raised bed of any size?
Yes. You set the bed dimensions — 4×4, 4×8, 2×8 or a custom size — and Niwa draws the square foot grid to match. You can keep several beds and several gardens in the app at once and switch between them.
Raised bed plannerHow does Niwa know when I should plant?
Niwa uses your location to find your average last spring frost and first autumn frost, then works backwards from those dates for every crop in your bed. Each plant gets its own sow-indoors, transplant and harvest window on a month-by-month timeline, so the dates are yours rather than a generic zone table.
How the planting calendar worksDoes Niwa warn me about bad companion plants?
Yes. As you place plants on the grid, Niwa puts a green dot between neighbouring squares that benefit each other and a red dot between squares that are better kept apart, so you see the conflict while you are still planning.
Companion planting in NiwaHow much soil do I need to fill a raised bed?
Multiply length × width × depth in feet to get cubic feet, then divide by 27 for cubic yards. A 4×8 bed at 12 inches deep needs 32 cubic feet, roughly 1.2 cubic yards or sixteen 2-cubic-foot bags.
Raised bed soil calculatorDoes Niwa work offline, and do I need an account?
The whole plant library and all your layouts are stored on the device, so the app works with no signal — useful on an allotment. There is no account to create and your garden data is never uploaded to a server.
See what's includedWhich growing zones and countries does Niwa support?
Niwa works worldwide. It recognises USDA hardiness zones in the United States and derives frost dates from your location elsewhere, including the UK, Canada, Australia and Europe.
Find your frost dates and zoneHow is Niwa different from other garden planner apps?
Three things: it is a native iPhone app rather than a desktop planner viewed in a mobile browser, it shows companion-planting conflicts on the grid as you place plants instead of in a separate chart, and it works fully offline with no account.
Compare Niwa with other plannersIs Niwa available on Android?
Not yet. Niwa is a native iPhone app and needs iOS 18.0 or later. An Android version is not currently available.
Read the gardening guides in the meantime