The quantity calculator

Every item in the bill of quantities needs a quantity, and the quantity calculator decides where it comes from. In the next few minutes we'll go through every method, how formulas work, and how the number is adjusted before it's priced.

The calculator has three parts. Down the left, the ways to get a quantity. In the middle, the one you're working on. And underneath, Adjust: wastage, item size and rounding.

There are five methods, and each one shows what it would give right now. Manual, a number you type. A take-off field. Another item. A calc sheet. Or a formula. The one this item uses is marked In use.

This slab uses a calc sheet, like a dimension book. Each line multiplies times, length, width and height, and the lines are added up. A box you leave empty counts as one, so the same sheet does lengths, areas and volumes.

The minus makes a line a deduction. The stair void comes off rather than adding on, and it stays on screen, so anyone checking the bill can see it was allowed for.

Add a line and type the sizes. Any box takes a sum, like two point four times three, and the total follows as you type. The bin at the end removes a line.

Take-off field follows a measurement. Fields are grouped by assembly, each with what it measures now. Point an item at the slab area, and it follows every revision of the drawing. One field can feed many items.

Another item takes its quantity from something else in the estimate: mesh chairs from the mesh, bedding sand from the slab. The item you're on is greyed out, and a switched-off item would count as zero.

Then choose to take that item's quantity with its wastage, or without. Take it without when this item carries its own allowance, so waste isn't counted twice.

Formula is the most flexible. Its inputs are variables: take-off fields or other items, each with a letter. Here A is the slab area and B the porch. Add the slab perimeter, and it becomes C.

Write the sum with the letters, using the insert buttons or the keyboard. Plus, minus, times, divide and brackets work as usual, and the result box works it out as you type.

Functions do the rest. Select part of the formula and press Ceiling, and that part goes inside the brackets, rounded up to the next whole number. Floor, round, min and max work the same way.

IF gives one answer when something is true, and another when it isn't. Here, if the slab is over a hundred and fifty square metres, add five per cent; otherwise leave it. Then add the porch.

Read the result box. A letter that isn't in the list, or a bracket out of place, is shown before you save. And whole numbers divide as whole numbers: write ten point oh divided by three, not ten divided by three.

Once a formula works, copy its variables and formula from the menu, and paste them onto other items in the same job, instead of building them again.

Under Adjust, wastage is added on top of whatever the method gives. Ten per cent makes this slab one hundred and ninety-seven point eight two. Keep it here, so the measurement itself stays an honest record of the drawing.

Rounding decides how the number is presented. Exact leaves it alone. Round up goes to the next whole number. There are round-ups to one or two decimals, for things ordered in part units, and round down. Wastage always comes first.

The three size options turn a measurement into what you buy. Type the size, say a mesh sheet of fourteen point four square metres. By size, rounded up, gives the sheets to order. Into size gives the square metres you will actually receive.

The bar along the bottom shows the whole journey, step by step: what the method gives, the wastage, the rounding, and the quantity the bill of quantities will show, with what it costs.

Save, and the bill of quantities updates, with anything that reads this item. To choose a method, work down: measure it if you can, follow another item if it's the same thing, use a formula if it's worked out from others, a calc sheet if you only have dimensions, and type a number only as a last resort.