Rule of Thirds Grid Overlay Tool: Free Online Calculator

How to use a rule of thirds grid

The rule of thirds splits an image into nine equal parts with two vertical and two horizontal lines. Placing your subject on a line, or where two lines cross, usually gives a more balanced picture than placing it in the exact centre. To use the tool, enter the width and height of your image, or add your photo and the size is filled in for you. The lines and their pixel positions update straight away.

Reference charts

Line positions for common image sizes (rule of thirds)

Thirds, golden ratio and quarters on a 1920 × 1080 image

Solved examples

Example 1: Full HD video frame, 1920 × 1080

Step 1: 1920 ÷ 3 = 640, so the vertical lines are at x = 640 and x = 2 × 640 = 1280.

Step 2: 1080 ÷ 3 = 360, so the horizontal lines are at y = 360 and y = 720.

Step 3: The four intersections are (640, 360), (1280, 360), (640, 720) and (1280, 720). Each section is 640 × 360 px.

Example 2: Portrait social post, 1080 × 1350

Step 1: 1080 ÷ 3 = 360, so the vertical lines are at x = 360 and x = 720.

Step 2: 1350 ÷ 3 = 450, so the horizontal lines are at y = 450 and y = 900.

Step 3: In a portrait, the eyes usually sit near the upper line, y = 450, about one third down from the top.

Example 3: Golden ratio grid on a 3000 × 2000 photo

Step 1: 3000 × 0.382 = 1145.90 and 3000 × 0.618 = 1854.10, so the vertical lines are at those x values.

Step 2: 2000 × 0.382 = 763.93 and 2000 × 0.618 = 1236.07, so the horizontal lines are at those y values.

Step 3: The middle column is 1854.10 − 1145.90 = 708.20 px wide, and the middle row is 1236.07 − 763.93 = 472.14 px tall. The centre section is smaller than the outer ones.

Common confusion: thirds, golden ratio and rounding

People often mix up the rule of thirds and the golden ratio grid. The rule of thirds uses equal sections, with lines at 33.33% and 66.67%. The golden ratio grid, also called the phi grid, pulls the lines closer to the centre, at 38.2% and 61.8%, so the middle section is smaller. The two are close enough that either works as a guide, and neither is a strict rule.

Another source of confusion is rounding. Most sizes do not divide evenly by three, so a 1280 px width gives a line at 426.67 px. Image editors round this to the nearest pixel, which makes no visible difference. The grid is also a guide for composition, not a requirement: centred subjects and symmetrical scenes often look best when you break it.

Frequently asked questions

What is the rule of thirds?

It is a composition guideline that divides an image into nine equal parts using two vertical and two horizontal lines. Subjects placed on the lines or at their crossings tend to look more balanced and interesting.

What are the intersection points called?

They are often called power points or crossing points. There are four on a thirds grid. Many photographers place the main subject, or a subject’s eyes, near one of them.

Can I add the grid to my own photo?

Yes. Choose a file in the photo field and the grid is drawn over it. The photo is processed in your browser and is not sent to a server. Very large photos are scaled down so the longest side is 4000 px.

How do I save the image with the grid?

Select “Download PNG”. The file contains your photo, or the blank canvas, with the grid lines on top.

Should I always follow the rule of thirds?

No. It is a starting point. Symmetry, leading lines and centred portraits can all work well. Use the grid to check a composition, then decide if breaking it improves the picture.

Which grid should I choose: thirds or golden ratio?

Start with thirds because it is simple and widely used. Try the golden ratio grid if you want lines a little closer to the centre. The difference is small, so pick the one that suits the image.

Results are estimates for composition guidance only; check official specifications and records for print, licensing or legal matters.