How to Build a Raised Garden Bed (Free Calculator + Cut List)
Quick answer: Here’s how to build a raised garden bed that lasts: level the site and strip the topsoil, then lag-screw 2×10 pressure-treated boards to 4×4 corner posts in a staggered pinwheel pattern — two rows for 18½″ walls, posts anchored 12″ into the ground. Line the inside walls with plastic, lay weed barrier underneath, and fill with ⅓ topsoil, ⅓ compost, ⅓ garden soil. The calculator below turns your exact dimensions into a full cut list and soil order. Documented by Jamison Rantz.
We built these two 12×4 beds in 2021, and they’ve fed us every summer since. This is the best version of a raised bed I’ve built in over a decade of doing this: staggered corners that can’t pull apart, walls that don’t bow, and posts anchored into the ground so nothing shifts. The guide below walks through the whole build — and the calculator turns your dimensions into a custom cut list and soil order, so you can skip the math.
Size your bed: soil + cut list calculator
Enter your dimensions and get the exact soil to buy (cubic feet, cubic yards, and bags) plus a complete cut list and shopping list, built the same way as the beds in this guide. For the full soil math and common-size charts, see the raised garden bed soil calculator page.
Enter your bed size and get exactly how much soil to buy — cubic feet, cubic yards, and bags — plus a custom cut list to build the bed at your dimensions, the same way I built ours. No sign-up needed to see your results.
A common fill is roughly ⅓ topsoil, ⅓ compost, ⅓ garden soil. Bulk soil is sold by the cubic yard (27 cu ft).
Your custom cut list — for 12' × 4' × 18½", ×1
| Part | Qty | Length | Material |
|---|---|---|---|
| Long wall boards | 4 | 12' | 2×10 board |
| End wall boards | 4 | 4' | 2×10 board |
| Corner posts | 4 | 2' 6½" | 4×4 post |
| Anti-bow cleats | 2 | 1' 6½" | 2×4 |
Corners are staggered ("pinwheel") — every board is cut to the full stated dimension and overhangs its corner post so the next wall butts into it. That means a 12 ft bed uses full 12 ft boards with zero cutting; the finished outside dimension runs about 1½" larger each way. Posts run 12" longer than the bed height to anchor into the ground. Line the inside walls with plastic sheeting before filling.
📩 Email me my cut list + build guide
Get this exact cut list and soil order for 12' × 4' × 18½" sent to your inbox, with the full step-by-step build guide — free.
Note: Soil and lumber figures are planning estimates using actual (not nominal) board dimensions. Confirm quantities before purchasing.
A free tool from Rogue Engineer. Be safe and happy building.
Tools & materials
A note on pressure-treated wood in vegetable gardens: modern PT lumber is copper-based, not the old arsenic formulas, and is rated safe for raised vegetable beds — it’s what we used. If you want to dig into the research, Fine Gardening and the University of Maine Extension both cover it well. If cedar or cypress is affordable where you live, it’s a great option too. Either way, lining the inside walls with plastic sheeting protects the wood, keeps soil from seeping through the cracks, and adds separation between soil and lumber.
How to build a raised garden bed, step by step
Step 1 — Pick the spot and prep the ground
Vegetables want 6–12 hours of full sun, and you’ll water this bed constantly — so pick a sunny spot within easy reach of a spigot. Mark the bed footprint with a tape measure and spray paint.
Strip the topsoil inside the footprint and cut a clean vertical edge. Getting the grass and topsoil out means weeds can’t grow up into the bed, and it gives you solid, level ground to build on.
Step 2 — Stain the boards first (optional)
Pressure-treated lumber doesn’t need a finish, but our beds sit next to the house, so we wanted them to look good. Staining the boards flat on sawhorses before assembly is far faster than cutting in against the ground later. We ran the stain just a little way down the inside faces too, so the wood looks finished above the soil line.
Step 3 — Build the first row
Start at the highest corner of your site. Set one end of a full-length board on the ground, clamp the other end to a 4×4 post, and get it perfectly level. Then drive two lag screws through the board into the post. Work your way around the box the same way: level each board, then lag it.
The corner trick that makes these beds strong: stagger the joints pinwheel-style. Each board sits flush with the post on one end and overhangs it by 1½″ on the other, so the next wall butts into that overhang. Every corner locks the one before it — and every board is cut to the full stated dimension, which means a 12 ft bed uses uncut 12 ft boards straight off the rack.
Building level boxes on ground that isn’t level leaves a gap under the low side. Rather than burying the bottom board, I laid a board along the gap, marked the taper at each end, and cut it with a circular saw — a tapered filler board closes the gap cleanly.
Step 4 — Stack the second row and cut the posts
With the first row done, measure and cut each 4×4 off at what will be the top of the next row, then repeat the same level-clamp-lag process for row two, keeping the pinwheel stagger going.
On beds 8 ft and longer, add 2×4 cleats inside the box, tying the two walls together mid-span. Without them, a long wall of wet soil will slowly bow outward. The calculator adds these for you automatically on longer beds.
Step 5 — Line it, then fill it
Staple plastic sheeting to the inside walls (protects the lumber and keeps soil and water from seeping through the cracks) and lay weed barrier under the bed. Leave the bottom open to the ground — the bed has to drain.
For soil, the mix that’s served us well is roughly ⅓ topsoil, ⅓ compost, ⅓ garden soil. A 12×4 bed like ours takes about 67 cubic feet — 45 bags, or 2½ cubic yards — and at that volume bulk delivery or a pallet beats hauling bags. Get your exact numbers from the soil calculator, and if you want to stop buying the compost third, our double compost bin keeps the beds fed for free.
Step 6 — Make it water itself (the upgrade we’d never undo)
The single best decision we made with these beds was automating the watering: a buried ½″ line from the spigot, micro sprayers in each bed, and a hose timer running daily waterings. Plants don’t die when life gets busy. The full irrigation setup — trenching, parts list, sprayer layout, and the timer settings we use — is its own guide: DIY raised garden bed irrigation.
Around the beds we laid weed barrier and stone with stepping stones between the boxes — no mowing, no mud, no bare feet on gravel.
Step 7 — Plant and enjoy
Most vegetables want 18–24″ of space, which put about 24 plants across our two beds. Plant, water, and enjoy — there’s nothing like cooking with vegetables you grew yourself.
If you build one, post a photo in the comments — and comment with any questions or lessons learned for the next builder. If deer or rabbits treat your garden like a buffet, the welded wire garden fence we put around ours has kept them out for years.
Be safe and happy building.
— Jamison
I just started the build to surprise my wife, I have all of my boards cut and I am struggling with screwing them together as shown in Step 1. If the boards are 4×6 and the screws are 4″, I am not sure how they screw together? Thanks for the help and enjoy the site. I can see many projects in my future.
I like this design. I built a raised bed a few years ago, but used 1 inch cedar boards from Home Depot. The thicker stock you’re using will work much better. I also had a deer problem which may not be a problem everywhere. I looked into getting a small electric fence. After a little more research I decided to add 3 rows of 30 pound monofilament fishing line around the bed (supported on metal posts), leaving a small inner buffer for me to walk. So far, I haven’t had any problems with the deer. Downside, is it does detract from the look of the raised bed. But it works.
Great tutorial! And great you got your little helper involved.
Thanks! We built these raised beds at our old house and luckily since it was in a neighborhood we didn’t have a deer problem! However, we now live out in the country and planted a big garden this year. We have learned a few tricks to help keep the deer away, along with a fence around the garden we have a motion activated deer deterrent. We also have tired a couple other things, like human hair around the garden edges (ask your local barber) and cut up irish springs soap and tied in a cloth and hung on the fence posts. Something about the smell is supposed to keep deer away. It’s hard to say what is working, but we haven’t had a deer problem so far!
I don’t know if the fishing line is the solution or not. I’ve been told that they can’t see the monofilament but they bump into it. Supposedly it creates an uncertainty about what they are jumping over and into. I think this probably works best on smaller raised beds. My dad has a large garden and he uses an electric fence which seems to work. But if the fence goes out for an extended time they quickly adapt and don’t hesitate to jump over.
Hello! Love the site and these plans. My hubby and I built these a few weeks ago and they look great. Only issue we’ve had is that the top boards are separating. Any ideas on how to fix this?
This looks awesome. One option would be to add a metal bracket to help keep the corners from separating.
Hey, I just found your site and am loving it so far! As I was reading through this, I noticed your Amazon referral links have an extra space between the backslash and ASIN, thus not correctly redirecting to the listing. I know this probably helps pay for the upkeep on the site so I wanted to let you know.
Outside of that, this is my favorite garden bed plan I’ve found so far. When my backyard is ready I think I’m going to try this out. Thanks for all the work you put in to making these!
Kyle, thanks so much for pointing that out. I am going to look into that. I appreciate you looking out for me, and glad you are going to try building from my plans!
Hey Jamie… Loved it !! This is exactly what i had been searching for – step by step guide to build a raised bed vegetable garden. Thank You !! 🙂
I got 2 questions here –
1) Drainage – i saw you covered the whole of bed with lining sheet – so the water will be trapped and wouldn’t drain out, is it? Isn’t drainage of water required for plants to flourish? Sorry if this question sounds like a silly one but I am no expert in planting- and curious to learn it these days. 🙂
2) I plan to make the same one on my apartment balcony – can I do this on a solid concrete floor as well?
I stay on 5th floor and have a big balcony – so really want to make something similar in there.
Looking forward for your guidance 🙂
Regards,
Shantanu
Thanks Shantanu! As far as drainage, the lining is just a weed blocker so it drains perfectly fine but keeps the weeds out. As far as putting it on a balcony, I’m not sure. I would be concerned about the weight (it is very heavy). But you say you have concrete floors so it may be okay. The other issue would be drainage. Mine drains out of the bottom into the ground. You having a concrete floor would not allow for that. You could add some weeping holes at the base though.
Seat around the top edge…GENIUS!
Thanks Cathy it’s been quite nice
First veggies picked from the garden. Proof that I may actually have a green thumb 🙂