How to Hang Pictures Perfectly Straight with Your Phone

The Problem with Hanging Things by Eye

Most people hang pictures by eye. They step back, tilt their head slightly, squint, and call it good enough. Two days later they're tilting their head every time they walk past it.

The issue is that our visual reference for "straight" is the room — and most rooms aren't perfectly square. Walls lean, ceilings dip, door frames bow slightly. When you hang a frame to match those imperfect lines, it looks right in context but is actually tilted relative to gravity. The moment you put something next to it, the difference becomes obvious.

A bubble level measures against gravity, not the room. That's the only reference that matters, and your phone can do it instantly.

What You Need

• Your phone with Bubble Level installed (free)
• A hammer and picture hook, or a drill and wall plugs for heavier items
• A pencil for marking
• Optionally: two-sided mounting strips (for lightweight frames with no hook)

Hanging a Single Picture Frame

Step 1 — Mark the Height

Hold the frame against the wall at the height you want it and mark the top corners lightly with a pencil. This gives you a reference to come back to after you've drilled or hammered.

Step 2 — Find the Hanging Point

Measure from the top of the frame down to the hanging wire or hook on the back. Note that distance. Add it to the height of your top-corner marks — that's where your wall hook needs to go.

Step 3 — Hang It and Check with the App

Once the hook is in and the frame is hanging, open Bubble Level and switch to vertical (portrait) mode. Hold the phone flat against the face of the frame — don't rest it on the top edge, press it gently against the glass or the frame face so you're reading the tilt of the frame itself.

The app shows the angle in real time. Slide one side of the frame up or down until you hit 0.0°. That's it.

If the frame keeps drifting back to a tilt, the wire on the back may be off-centre, or the hook is too smooth and the wire is sliding. A small piece of masking tape around the hook solves the latter in seconds.

Hanging Multiple Frames in a Row

A row of frames is where things get genuinely tricky. Each one being level individually isn't enough — they also need to be at the same height relative to each other, and evenly spaced.

Use a Long Reference Line

Use a long piece of painter's tape or a chalk line to mark a horizontal reference line at the height you want the bottom of all frames to sit. Check this line is level by placing your phone flat along it — the app should read 0.0°. Adjust the line until it does.

Now every frame that sits on this line is automatically level and aligned. Measure equal gaps between frames with a tape measure, mark your hook points, and hang away.

The Quick Two-Frame Check

For just two frames side by side, there's a faster method. Hang the first frame and level it with the app. Then, hold your phone across both frames at once (resting on the top edges) to check they sit at the same height. Adjust the second hook up or down until the reading matches the first.

Shelves

Shelves are easier than frames because you're usually working with brackets and can adjust before the screws are fully tight.

Fix one bracket first — don't fully tighten. Rest the shelf on it. Place your phone flat on the shelf surface and use the flat (landscape) mode in the app for a live angle readout. Pivot the free end of the shelf up or down until you hit 0.0°, then mark the second bracket position, remove the shelf, drill, and mount. The result is a shelf that's level against gravity, not just visually straight.

For longer shelves (over a metre), check at both ends and the centre — a shelf can bow slightly, and what reads level at one end may be off by half a degree in the middle.

Mirrors

Large mirrors are heavy and often have only one hanging point at the top. Once hung, hold the phone vertically against the side edge of the mirror frame to check the tilt, then gently rotate the mirror around its single hook until the app reads 0.0°. Use a small wedge of cardboard behind one bottom corner to hold it in place if the mirror tends to drift.

Cabinets and Flat-Pack Furniture

Wall cabinets need to be both level (left-to-right) and plumb (front-to-back) or doors will swing open or closed on their own. Check the top surface of the cabinet with the phone in flat mode for the left-right level, then check the side face of the cabinet in portrait mode for the plumb. Most wall cabinet brackets have a small adjustment screw — a Pozidriv screwdriver and thirty seconds is usually all it takes to get both readings to 0.0°.

For flat-pack furniture assembled on the floor — bookcases, wardrobes — the same principle applies. Place the phone on each horizontal surface before tightening the final screws, and use the adjustable feet if available. Furniture that sits level from the start is far less likely to develop squeaks, wobbles, or doors that won't stay closed.

One Tip That Saves Half the Work

Before hanging anything, calibrate the app on a known level surface. A window sill or kitchen worktop that you've already confirmed is flat works perfectly. Tap the calibration button in Bubble Level to zero out any sensor drift. Takes three seconds and means every reading you take that day is accurate.

The Takeaway

Your phone's accelerometer measures gravity. Gravity is perfectly consistent everywhere in your home. That makes your phone, with the right app, more reliable than a cheap spirit level and quicker to use than a laser level for most household jobs. The only thing it takes is remembering to open the app before you put the nail in the wall rather than after.