Fields, items, formulas and calc sheets

Open Calculate Quantity on any BOQ item and you choose one of five sources for its quantity. This article covers all of them in detail, and the two things that happen to the number afterwards.

If you only want to know which method to reach for, read Getting a quantity instead — it is the short version.

The five methods

The buttons across the top pick the method. The one currently in use is teal.

Button	Quantity comes from	Follows changes
Manual	A number you type	No
Field	A take-off measurement	Yes
Item	Another item in this costing	Yes
Calc Sheet	Dimensions entered as rows	Recalculates from the rows
Formula	An expression over named variables	Yes

An item uses one method at a time. Switching method does not erase the others — a calc sheet you built stays there if you switch to Formula and back — but only the selected one produces the quantity.

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Field

Calculate quantity using a field. The quantity comes from a take-off field, so it follows every measurement you make on the drawing.

Select Field is a searchable tree of the costing’s take-off fields, grouped by assembly. Pick one and the item’s quantity becomes that field’s total.

Measure on the plan

The button at the bottom of this tab opens Take-Off with this item in mind.

Measure into an existing field or create a new one, press Done, and the item comes back already pointed at what you measured. It saves doing the two halves — measure it, then price it — as separate errands.

What to know

• A field’s total is read live. Change a measurement and the item is already right; there is no recalculation to run.
• One field can feed many items. Measure the slab once and point the concrete, the mesh, the membrane and the sand bed at it.
• A field that gets its quantity from a formula is read-only in Take-Off. The formula wins; clear it if you want to measure the field off a drawing instead.

See Take-off fields and the BOQ for how fields, units, heights and depths work.

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Item

Calculate quantity using the quantity of another item in this costing. This is the one people miss, and it removes a lot of duplicated measuring.

Two pickers:

1. Select Code Center — which cost centre the source item lives in.
2. Select Item — the item itself.

The quantity becomes that item’s final calculated quantity — after the source item’s own wastage and rounding have been applied. You are borrowing the number the source item ended up with, not its raw input.

When to use it

Whenever one item’s quantity genuinely is another’s:

This item	Takes its quantity from
Mesh chairs	The mesh
Bedding sand	The slab area
Paint, second coat	Paint, first coat
Skirting adhesive	Skirting
Door furniture	Internal doors

It is faster than a formula when the relationship is one-to-one, and it survives being re-measured because it reads the source item rather than a copy of it.

The source item must stay switched on

If the item you are borrowing from is switched off, this item’s quantity becomes zero — silently. Nothing warns you.

That bites when you carry options: switch off the tiled roof in favour of colorbond, and anything that took its quantity from a tiled-roof item quietly drops to nothing. If you price options this way, check what depends on them before switching.

Chains

The source item can itself take its quantity from a field, a formula or another item, and it all resolves. Measure the slab once, let the concrete read the field, and let the pump read the concrete.

Keep chains short. Two links is easy to follow; five is a puzzle when a number looks wrong six weeks later.

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Formula

Calculate quantity using the Formula. The quantity is an expression over named variables you define on the item.

The tab has three parts: the toolbar, the formula box, and the variables grid.

Toolbar button	Does
Add variable	Adds a row to the variables grid
Quick add all	Brings in the available variables in one go
Delete all variables	Clears the grid
Copy Variables / Paste Variables	Moves a set of variables to another item

Type the expression into the box, then press the = button to see the result before you save. That check is worth taking — a formula that produces 1,864 instead of 18.64 looks entirely plausible sitting in a total.

Writing one

Ordinary arithmetic over your variable names: +, −, ×, ÷ and brackets.

Item	Formula	Reads as
Slab mesh	SlabArea * 1.05	Slab area plus 5% laps
Slab concrete	SlabArea * SlabDepth	Area × depth
Wall paint	WallLength * WallHeight * 2	Both faces
Skirting	WallLength - DoorOpenings	Wall run less the doors

Name variables so the formula reads like a sentence. SlabArea * SlabDepth is obviously right; A1 * D is not, and you will not remember what D was.

Copy and paste variables

The copy/paste buttons are what make formulas practical across a bill. Set up a variable set on one item, then paste it onto the others that need the same inputs rather than rebuilding it each time.

See Formula fields for more worked examples.

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Calc Sheet

Calculate quantity using the Calc Sheet. The dimension book: a grid of rows that multiply out and total.

Toolbar button	Does
Add new line	New row
Delete all lines	Clears the sheet
Copy calc sheet / Paste	Moves a whole sheet to another item

How a row calculates

Each row is:

Times  ×  Length  ×  Width  ×  Height  ×  Factor  ×  (1 + Wastage)

Then the rows are added together.

Any dimension left at zero counts as 1. That is the rule that makes one grid work for lengths, areas and volumes alike — fill in only the dimensions that apply and leave the rest blank.

You want	Fill in
A length	Length
An area	Length and Width
A volume	Length, Width and Height
A count	Times only

Deductions

A row marked as a deduction is subtracted rather than added — its result goes negative.

That is how you take out door openings, window reveals, a void in a slab. The deduction stays visible as its own line, which is the point: someone checking the bill can see the allowance was made.

Per-row wastage and rounding

Each row carries its own Wastage percentage and its own output method — Exact, Round Up or Round Down — applied to that row before the rows are summed.

Round Up per row is how you handle things bought whole. Eleven lengths of timber rounded up individually is not the same as the total rounded up once, and the row-by -row version is usually the honest one.

Worked example

Skirting to four rooms, from a room schedule:

Description	Times	Length	Width	Deduct	Result
Living perimeter	2	9.60	—		19.20
Bed 1 perimeter	2	6.80	—		13.60
Bed 2 perimeter	2	6.40	—		12.80
Hall	2	6.80	—		13.60
Door openings	7	0.87	—	●	−6.09
					53.11 m

Width and Height are blank, so they count as 1 and the sheet returns a length.

The door deduction is the reason to use a calc sheet at all. It is on the screen, it is explicit, and anyone checking the bill can see it was allowed for.

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Manual

Calculate quantity using manual entry. Type the number into Input Quantity.

Right for genuine one-offs — a call-out fee, a lump sum, a figure you were given over the phone. Wrong for anything measurable, because nothing will ever update it.

Flag anything you type

Typed quantities are the ones that go stale when a drawing is re-issued, and nothing marks them. If you have to type a number for something that really should be measured, put a Flag on the item so you can find it again before you submit.

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What happens to the number afterwards

Whichever method produced the quantity, two things are applied on top, in this order.

1. Wastage

Quantity × (1 + Wastage / 100)

Set on the item, next to the method buttons. Measure 100 m² with 10% wastage and the item carries 110 m².

Keep wastage here rather than building it into the measurement. The measured figure stays an honest record of what is on the drawing, and the allowance stays visible and adjustable across a whole trade.

2. Output — rounding

The Output dropdown decides how the result is presented. Eight options:

Output	What it does	Result for 18.64
Exact	Leaves it alone	18.64
Round Up	Up to the next whole number	19
Round Up to 1 Decimal	Up to the next tenth	18.7
Round Up to 2 Decimals	Up to the next hundredth	18.64
Round Down	Down to the whole number	18
Into Size	Up to the next whole multiple of the size	see below
By Size	Divides by the size	see below
By Size Rounded Up	Divides by the size, rounds up	see below

Wastage is applied before rounding, not after. So 100 m² with 10% wastage and Round Up gives 110, not 111.

The two decimal options round up, never to nearest: 18.641 becomes 18.65, not 18.64. A figure that is already at or under that many decimals is left alone, which is why 18.64 above is unchanged by Round Up to 2 Decimals. Use them for materials measured to a part-unit but ordered in sensible increments — concrete to the tenth of a cubic metre, for instance — where Round Up to a whole unit would overstate the order and Exact carries more decimals than anyone orders in.

The three “size” options

These convert a measured quantity into how many you have to buy, using a size that comes either from the item or from its selected product — set by the Use Item Size / Use Product Size dropdown.

Say you have measured 47.5 m of timber and it comes in 4.8 m lengths:

Output	Maths	Gives	Means
By Size	47.5 ÷ 4.8	9.90	Lengths needed, unrounded
By Size Rounded Up	⌈47.5 ÷ 4.8⌉	10	Lengths to order
Into Size	⌈47.5 ÷ 4.8⌉ × 4.8	48.0	Metres you will actually buy

By Size Rounded Up is the one to use when you order in whole units — lengths, sheets, rolls, boxes. The item is priced per unit and the quantity is the number of units.

Into Size keeps the quantity in the measured unit but rounds it up to what you will actually receive. Use it when the item is priced per metre or per square metre but supplied in fixed sizes.

A size of zero is treated as 1

If the size field is empty or zero, the calculation falls back to 1 — so By Size returns the quantity unchanged and looks like it is not working. If a size option seems to do nothing, the size is missing.

Saving this screen updates dependent formulas

Every method on this screen produces a quantity, and so do wastage, size and rounding. Any of them can move a formula elsewhere in the costing that reads this item.

So when you press Save, the BOQ recalculates those formulas for you a moment later, the same as it does after an inline quantity edit. There is nothing extra to click. See Keeping formula results current.

If you save the Formula tab with a formula the system cannot read, it says so on the screen and stores the item’s quantity as zero. Closing the screen does not make that go away: a Formula needs attention warning stays on the BOQ toolbar, and clicking it brings you straight back here to fix it.

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Choosing a method

Work down and take the first that applies:

1. Can it be measured off a drawing? → Field. It follows every revision.
2. Is it the same as another item’s quantity? → Item.
3. Does it derive from other quantities? → Formula.
4. Do you have dimensions but no drawing to measure? → Calc Sheet, so the working is recorded.
5. Otherwise → Manual, and flag it.

When a quantity looks wrong

It is zero and you did not expect it. If the method is Item, check the source item is switched on — a switched-off source gives zero with no warning.

A size option is doing nothing. The size is empty or zero, so it falls back to 1. Check whether the item is set to use the item size or the product size, and that the one it is using has a value.

The number is bigger than the measurement. Wastage is applied before rounding — check the wastage percentage before assuming the rounding is wrong.

It did not change when you measured. The item is probably not on the Field method, or is pointed at a different field. Reopen Calculate Quantity and check which button is teal.

A formula gives a plausible but wrong answer. Press = and check the result against a rough mental figure. A misplaced decimal survives every other check.