There are several ways to measure a room with an iPhone:
Built-in Measure App (Easiest)
Your iPhone has a free built-in app called "Measure" that uses AR (augmented reality):
Open the Measure app (pre-installed on iPhone with iOS 12+)
Point your camera at the floor and move your iPhone around slowly to let it detect the space
Tap the + button at points you want to measure between
For room dimensions, tap at each corner to measure wall lengths
The app will show the measurement in real-time
Tips for accuracy:
Good lighting helps
Move slowly and steadily
Hold your iPhone vertically
Measurements are typically accurate within 1-2%
For Floor Plans: RoomScan App
RoomScan LiDAR (uses iPhone's LiDAR sensor on Pro models):
Automatically creates floor plans
Just touch your phone to each wall in sequence
Generates a scaled floor plan with measurements
For Event/Venue Planning: Magicplan
Magicplan is popular for event professionals:
Creates detailed floor plans
Add furniture and equipment
Export to PDF or CAD
Free basic version available
Which iPhone Models Work Best:
iPhone 12 Pro and newer - Have LiDAR sensors for most accurate measurements
iPhone with iOS 12+ - Can use standard Measure app (good for basic measurements)
The built-in Measure app is probably the quickest solution for capturing basic room dimensions during site visits. For full floor plans, Magicplan would be the professional choice.