Guide

AI and phone apps for measuring rooms and estimating materials

16 October 2026Shaun, 20+ years in UK construction

Phone apps for measuring rooms, British Gypsum's plaster calculator, and why a photo is not a board order. UK prices from the makers.

A room that looks like four metres is often 3.7 once you put a tape on the skirting. The difference is a strip of board, a bag of finish, and an argument about the quote. A phone can hold a rough size. A manufacturer's calculator can turn sizes you typed into bags. Neither one has walked the room. If a draft adds a length you did not measure, the order is wrong before you leave the yard.

Figures below were read from each maker's own page on 16 October 2026. None of the links are affiliate links. This is not a list of which app is "most accurate". The makers do not publish a single millimetre claim you can take to a customer.

Shaun, 20+ years in UK construction, still checks a diagonal with a tape before he orders boards. We search the AI world every week so you don't have to. An app can store the sketch. It cannot stand in for the tape on a job you are pricing.

A tape, a phone, and a calculator do different jobs

The tape, or a laser measure you trust, is the measurement. You write down length, width, and height, and you note the doors, the windows, and the bit of wall that is out of square. That list is the only input the rest of the tools should see.

The phone app is a way to capture that list when you are alone and the notebook is in the van. Apple's Measure app and the LiDAR apps turn the camera into a rough tape. They are useful for a sketch and a photo of where you measured. They are a poor sole record for a staircase, a bay, or a ceiling with a bulkhead.

The calculator on a manufacturer's site does arithmetic on the sizes you type. British Gypsum's plaster calculator asks for height and width. It does not look at a photograph. A chat tool can lay your own measurements out as a cutting list. It must not invent a measurement, a waste percentage, or a bag count you did not work out.

The price of the job is a separate decision. The quoting guide is where the scope and the figure go, after the quantities exist. The quoting apps guide covers software that stores the quote. Measuring the room is earlier than both.

Apple's Measure app, and what LiDAR changes

Measure is the app already on an iPhone, in the Utilities folder. Apple's iPhone guide (opens in a new tab) says you can measure nearby objects with the camera, pick up the edges of a rectangular object, or set the start and end of a line yourself. It says the best results are on well-defined objects 0.5 to 3 metres from the phone, and it says the measurements are approximate. That sentence is the caveat. Approximate is not a tolerance you can put on a quote.

On some models the same guide describes edge guides and a ruler view for a closer look at the line. Apple's Measure support article (opens in a new tab) says supported Pro models use a LiDAR scanner so objects are quicker to measure, and it lists iPhone 12 Pro and iPhone 12 Pro Max and later Pro phones, plus iPad Pro 12.9-inch from the 4th generation and iPad Pro 11-inch from the 2nd generation. A phone that is not on that list still opens Measure. It uses the camera. It does not gain the scanner because you downloaded an app.

There is no price. Measure is part of the phone. There is also no official millimetre accuracy on that page. Do not let a product video, or a chat tool, turn "approximate" into "accurate to 5 mm". If the wall is in poor light, if you are too close or past 3 metres, or if the end point is a blurry corner, measure it again with a tape. Save the photo Measure offers, and write the number you will actually use next to it. The photo is the record of where you stood. The number you type is the order.

magicplan: pounds in the App Store, dollars on the website

magicplan is a floor-plan app. Its UK App Store page (opens in a new tab) listed these in-app purchases on 16 October 2026: Sketch at £12.99 a month or £129.99 a year, Report at £39.99 a month or £399.99 a year, and Estimate at £89.99 a month or £899.99 a year. Those are Apple's UK prices for those plans. They include VAT in the way the App Store usually shows a price. Read the plan name before you subscribe. Estimate is not the same product as Sketch.

The company's own pricing page (opens in a new tab) describes a different shape of plan. It says plans start at 10 new projects a month, that unused project credits roll over, and that users are not charged extra. It says LiDAR scan is available on iOS Pro devices, alongside manual and laser-assisted measurement. If you go over the projects in the plan, it says the extra project is added at $40. That figure is in US dollars on the page, not pounds. This guide will not convert it. Your card provider will, and the rate will move.

The help page on LiDAR and Auto-Scan (opens in a new tab) says Auto-Scan needs a device with a LiDAR sensor using Apple's room tools, and that this was limited to iPhone 12 Pro or Pro Max and later, or iPad Pro, on iOS 17 or later. If your phone is not on that list, you still have manual measuring and a Bluetooth laser, which the same help centre describes for sketching. A laser you already own, pointed at a corner you can see, is often the better number.

magicplan can hold photos, notes, and an estimate built from a price list you put in. The estimate is only as good as that list and the floor plan under it. A price list in the app is not a survey. If the plan says a wall is 4.2 metres and your tape says 4.05, change the plan before you trust the material total.

Plaster bags and plasterboard sheets, from the maker

British Gypsum's plaster coverage calculator (opens in a new tab) asks you to pick a product and type the height and width of each wall, ceiling, or opening. It estimates area and bags. It does not accept a photo. You need the sizes first.

For a skim, the Thistle MultiFinish data sheet (opens in a new tab) says coverage is 10 square metres per 25 kg bag at 2 mm thick, on walls and ceilings. It says the water requirement is 11.5 litres a bag. The White Book notes that 2 mm is for flat surfaces, and that a very uneven wall should be dubbed out with an undercoat rather than buried in finish. A blown wall is not a 2 mm job. Do not order "10 square metres per bag" for a wall you have not checked with a straight edge.

Board sizes are on the product page, not in a chat. Gyproc WallBoard 12.5 mm (opens in a new tab) is sold in more than one sheet. The range includes 1200 mm by 2400 mm, and also longer sheets such as 2700 mm and 3000 mm, plus narrower 900 mm boards. A 1200 by 2400 sheet is 2.88 square metres. That arithmetic is the sheet, not your room. Openings, cuts, and a ceiling pattern change how many sheets you carry upstairs. The data sheet also allows the width to be up to 4 mm under nominal and the length up to 5 mm under. You still set out from the wall you measured, not from the nominal sheet, when the cut is tight.

A chat tool can turn a list you typed into "walls, ceiling, openings, sheets of 1200 by 2400". It cannot see the hob, the consumer unit, or the fact you want the joints to miss a socket. Add waste only as a number you chose. If you want 10% for cuts, type 10%. If you do not type it, the draft must not insert it.

A photo is not a quantity

Several apps, including magicplan, let you photograph the room and pin the picture to the plan. That is a record for you and for the customer. It is not a measured bill of quantities. A model built from photos, or from a quick LiDAR pass, still has to be checked against a tape on the lengths that decide the order: the longest wall, the ceiling height at both ends, and the openings.

Apple says Measure is approximate. magicplan does not publish a millimetre tolerance on the pages above. A research paper about phone LiDAR is not a specification for your quote, and this guide will not borrow one. If the job is a kitchen run, a staircase, or anything another trade will build from your sizes, measure those lines twice and write both down. If they disagree, the tape wins.

Do not upload a customer's face, a letter on the sideboard, or a screen showing their address into an app whose account you share with a crew. The room is enough. The free tools guide makes the same point about what stays out of a chat.

Turn these measurements into a material list. UK English. Metres. Use only the numbers I type.

Rules:
- Do not change a measurement. Do not fill a gap.
- Do not add a waste percentage unless I type one.
- Plaster: Thistle MultiFinish, 10 square metres per 25 kg bag at 2 mm, only if I say the wall is flat enough for a 2 mm skim.
- Boards: 1200 by 2400 mm Gyproc WallBoard is 2.88 square metres a sheet. Say how many full sheets the area needs, and leave the cuts as offcuts I must check.
- If a length is missing, write MISSING. Do not estimate it.

Room:
Wall lengths and heights:
Ceiling:
Openings to deduct:
Waste I want, or "none":
Flat enough for a 2 mm skim? Yes or no:

Read every figure against your notes before you text a merchant. A tidy list with one invented length is a wrong order. The number you are willing to stand behind is the one on the tape, not the one that made the paragraph flow.

Common questions

Is Apple's Measure app accurate enough to order boards?

Apple says the measurements are approximate, and that the best results are on well-defined objects 0.5 to 3 metres from the phone. Use it for a sketch. Check the lengths that decide the order with a tape before you buy.

Which iPhones have the LiDAR scanner Measure uses?

Apple's Measure support article lists iPhone 12 Pro and iPhone 12 Pro Max and later Pro phones, plus stated iPad Pro models. Other iPhones still open Measure with the camera. They do not gain the scanner.

How many square metres does a bag of Thistle MultiFinish cover?

British Gypsum's data sheet says 10 square metres per 25 kg bag at 2 mm thick, on a flat wall or ceiling, with 11.5 litres of water. A very uneven wall is not a 2 mm skim. Their calculator needs the height and width you measured.

What does magicplan cost in pounds?

On 16 October 2026 the UK App Store listed Sketch at £12.99 a month or £129.99 a year, Report at £39.99 or £399.99, and Estimate at £89.99 or £899.99. The website's project plans bill extra projects at $40, which is not a pound price. Read the plan in the app before you pay.