Raised Bed & Sleeper Calculator – Timber, Soil & Cost
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Raised Bed & Sleeper Calculator
Plan rectangular bed walls, timber courses, corner cuts and internal capacity, with optional fill, fixings and job pricing.
YOUR ESTIMATE
Your raised bed estimate
Cut schedule, timber purchases and internal fill quantities.
Enter timber and bed dimensions, then calculate.
Inputs changed. Calculate again to update your estimate.
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Link the sleeper cut list to the soil order
Use outside dimensions for the timber layout and the calculated inside dimensions for fill. Corner arrangement and actual sleeper thickness affect the usable planting space, so outside length × outside width is not the soil footprint.
For a separate supplier soil order, use the topsoil calculator with the checked internal fill quantity. Keep compost, drainage layers and existing fill separate where your specification calls for them. Do not add a full second bed capacity to a soil purchase already calculated here.
For surrounding features, use the fence materials calculator or the decking calculator. A gabion basket and stone estimate covers a different enclosure system, with its own supplied layout and fill materials.
Plan a raised sleeper bed from its outside dimensions
This free raised bed and sleeper calculator turns a rectangular layout into wall cut lengths, a practical stock cutting plan and the actual space available for soil. It is designed for open-bottom garden beds made from one timber cross-section, with square butt-joint corners. Enter the timber dimensions, outside bed size and number of courses to get a basic result. Soil purchases, fixing quantities and prices can be added when useful.
Several beds can share one estimate and one timber stock size. Add a row for each different size and use copies for repeated beds. Bulk entry accepts dimensions from notes or a spreadsheet. The result keeps bed names and course numbers so a combined shopping list does not lose the information needed to cut each frame.
Use finished timber dimensions in the correct orientation
Stock length is the usable length of a new sleeper or board. Deduct any damaged ends or trimming allowance before entering it. Wall thickness is the horizontal timber dimension from the outside face to the soil face. Course height is the vertical dimension of one layer. Turning a rectangular sleeper onto another face changes both values, and therefore changes the cut lengths, total bed height and soil capacity.
Use actual finished measurements rather than assuming nominal product dimensions are exact. All timber in one estimate shares these dimensions. If two beds use different cross-sections or stock lengths, calculate them separately so the cutting plan does not mix incompatible material.
The outside length and width describe the overall footprint, including the timber. Internal length and width each subtract two wall thicknesses. For example, a bed 2.4 m long and 1.2 m wide with 100 mm thick walls has an internal footprint of 2.2 m by 1.0 m. Using the outside footprint for soil would overstate the available space.
Choose which sides run through the corners
In the length-through arrangement, two pieces retain the full outside length. The other two fit between them, so each is the outside width minus twice wall thickness. Width-through reverses that relationship. The words length and width refer to the axes you entered; the calculator does not automatically swap them when the width is numerically larger.
Alternating direction switches the through pair on successive courses, starting with length-through at the bottom. This produces different cut lengths on odd and even courses, which are shown in the schedule. The result describes geometric butt joints only. It does not choose how courses connect vertically or how the wall resists soil pressure.
Each wall side is one continuous piece. If any required piece exceeds stock length, the calculator asks for a correction instead of silently adding a splice. A longer wall may be possible with a separately specified joint and support detail, but that detail changes both construction and material quantities. It should not be invented by a purchasing calculator.
Read the timber cutting plan
All cut lengths are collected, including bed copies and courses, then placed into stock sleepers longest first. Short pieces can share a sleeper when their combined length and the entered kerf fit. This reuses length offcuts across beds instead of rounding every wall piece to a whole sleeper.
Kerf is material removed by the saw blade. The model allows one kerf between adjacent finished pieces. The listed end remainder is measured before a final separating cut; a usable saved offcut can therefore be shorter by one kerf. Stock end trimming is excluded because the entered stock length is already usable. Check the plan against your actual cutting method and timber condition before marking out.
The longest-first plan is practical, but it is not guaranteed to use the fewest possible sleepers. Additional spare sleepers can cover your chosen contingency. Matching usable whole sleepers already owned are deducted from the calculated stock requirement plus spares. Part-used offcuts are not treated as whole stock. Price is per full sleeper, not per cut piece or metre.
Full capacity versus soil being purchased
The basic capacity uses internal footprint multiplied by wall height. Wall height is course count times vertical timber height. This reports the space up to the top of the walls from their base plane. It does not include ground excavation below that plane or subtract posts, liners and irregular internal details.
The optional growing-medium section subtracts a top gap and the height of a lower layer that you are not buying as growing medium. Those heights apply to every bed in the estimate. Their sum cannot exceed any bed's wall height. A lower layer is a geometric deduction only; it is not a recommendation to add rubble, drainage material or any particular soil arrangement.
An extra fill percentage applies after those deductions. Use it for an assessed allowance, rather than assuming every soil mix settles by one fixed amount. Volume-only mode gives a quantity to discuss with a supplier. Bag mode divides by the labelled volume and rounds up to whole bags before deducting usable whole bags already owned. Loose supply rounds to the supplier order increment you enter. Litres are used for metric bag volume and cubic feet for imperial bags.
A worked raised-bed example
Take one bed with outside dimensions 2.4 m by 1.2 m, 100 mm wall thickness, 200 mm course height and three courses. It is 600 mm tall and has 2.2 m by 1.0 m of internal space. Full capacity is therefore 1.32 m³.
With length-through corners on every course, the cut schedule has six pieces at 2.4 m and six at 1.0 m. With 2.4 m usable stock and zero kerf for this arithmetic example, the six short pieces share three sleepers, while the long pieces use six more: nine stock sleepers altogether. A real saw kerf should be entered before ordering and cutting.
If the top gap is 50 mm and a separately assessed lower layer is 100 mm, growing-medium depth becomes 450 mm. The base growing-medium volume is 0.99 m³. A 10% allowance gives 1.089 m³, which rounds up to 22 bags of 50 litres before deducting owned bags. These figures illustrate the calculation and are not a recommendation for a particular bed construction.
Fixings and optional job costs
The fixing section multiplies four corners per course by your specified fixing count, then applies bed copies and adds whole-project extra fixings. The result rounds up to purchase packs and deducts owned whole packs. No screw quantity or size is supplied as a universal default. Use the actual timber supplier or designed connection detail.
Separate supports, liners, brackets, delivery and preparation can be allowed under other whole-job costs. Labour can use one price per complete bed, hours or days. Time pricing is often easier when bed sizes or site preparation differ. Closing a pricing section retains its values. Turning fill or fixings off excludes those quantities and costs while preserving the inputs for later use.
All prices should use a consistent pretax basis. Markup is a percentage added to cost; it is not profit margin. Tax then applies to the selling price. Currency selection changes symbols only, while the measurement selector converts dimensions and relevant unit prices.
Construction guidance
For practical product context, consult Wickes sleeper techniques and the BSW sleeper guide. The RHS raised-bed guide covers broader planning considerations. Follow the selected product's current instructions and the actual site requirements.
The calculator does not specify timber treatment, safe wall height, foundations, post spacing, drainage or retaining-wall stability. Elevated planters with a load-bearing bottom, seating and structures supporting people need a different design assessment. Curved, mitred, stepped-footprint and shared-wall beds are outside this rectangular four-wall model.
Raised bed and sleeper calculator FAQs
Should I enter inside or outside dimensions?
Enter outside length and width. The calculator deducts the timber thickness on both sides to find internal space.
Can corners alternate between courses?
Yes. Select alternating direction. Odd courses use length-through and even courses use width-through, with each course listed in the cut schedule.
Why are some wall cuts shorter?
At a butt joint, a side fitted between the other walls loses twice their thickness. Ignoring that deduction makes the completed bed larger than intended.
Does it reuse sleeper offcuts?
It reuses calculated length remainders across the entered cuts, allowing kerf between adjacent pieces. It does not import irregular existing offcuts or guarantee an optimal plan.
Can I include soil bags?
Yes. Enable adjusted fill, select whole bags and enter their labelled volume. Optional top gap, lower-layer deduction and reserve are shown separately.
Does it tell me how many screws are safe?
No. It counts purchases from your specified fixing quantity. Suitable screws, supports and connection details must be selected separately.
Can I print the cutting schedule?
Yes. Print / Save PDF includes the bed breakdown, cut schedule, stock plan and any optional quantities and costs. The calculator and printout are free.
Related free calculators
Need a worked example? Read our Raised Bed Materials: Lumber Cuts and Inside Soil Volume before ordering.