Timber Stock Forms and Quantity Calculations
Timber comes in standard stock forms and sizes. Learn planks, dowels, mouldings and sheet materials, the difference between rough sawn and planed timber, and how to calculate how much to buy.
Justify the choices, the way you are assessed
Free interactive practice on the decisions the assessment actually asks you to justify.
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Buying timber wisely
Timber is not sold in any shape you like - it comes in standard stock forms and sizes. Knowing them lets you choose the right material and work out exactly how much to buy. This module covers the stock forms, the difference between rough sawn and planed timber, and the quantity calculations that stop you over- or under-ordering.
Stock form words
Four ideas run through the topic:
Match each stock form to its description
- Plank
- Dowel
- Moulding
- Sheet material
- A wide, flat length of solid timber
- A round rod, useful for pegs and rails
- A shaped strip, such as skirting or beading
- A large flat board like plywood or MDF
Why is it smaller?
Why is a piece of planed timber smaller than its nominal size?
- Planing removes material from each face
- It shrinks while sitting in storage
- It was measured incorrectly at the mill
- It is simply a cheaper grade of wood
Working out how much to buy
To calculate the timber for a job: 1. Total length = number of pieces x length of each 2. Stock lengths = total length divided by the stock length, then rounded UP to a whole number 3. Cost = number of stock lengths x price each Always round the number of lengths up - you cannot buy a fraction of a length.
Total length needed
A shelf unit needs 4 shelves, each 300 mm long. What total length of timber is needed, in mm? (Total length = number of pieces x length of each.)
Which are sheet materials?
Select the TWO that are manufactured sheet materials.
- Plywood
- MDF
- Dowel
- Moulding
Nominal to actual
A piece of timber has a nominal thickness of 25 mm. Planing removes about 4 mm in total. What is its actual thickness, in mm?
Rough sawn versus PAR
The same timber can be bought straight from the saw or smoothed all round.
How many lengths?
You need 5 pieces of 600 mm (3000 mm in total). Timber is sold in 2400 mm stock lengths. How many whole stock lengths must you buy? (Divide, then round UP.)
Put it together
Timber is sold in stock _____ such as planks and dowels. Rough _____ timber is cheaper; _____ timber is smoother but smaller than its _____ size. A _____ list records every piece you need.
Order the calculation
Put the steps of working out how much timber to buy into the correct order.
- List every piece needed, with its length and quantity
- Add up the total length required
- Divide by the stock length and round UP to whole lengths
- Multiply the number of lengths by the price each
- Read off the total cost
In the workshop
Three decisions about buying and using timber. Pick the best choice each time.
- You need smooth timber, ready to use, for a visible display frame. Which do you buy?
- You need 3000 mm of timber, sold in 2400 mm lengths. How many lengths do you order?
- Your design needs 25 mm thickness, but you buy 25 mm nominal PAR. What should you expect?
Build the cutting list
Top answers build a cutting list, total the length, and divide by the stock length - always rounding up to whole lengths, because you cannot buy part of one. They also allow for planing: if a design needs a finished size, remember PAR arrives a few millimetres under its nominal size. Cutting list, round up, allow for the actual size - top band.