Ratio Calculator

Free design ratio tools

Aspect, Golden & Scale Ratio Calculators

Resize images, split lengths by the golden ratio and convert real sizes to model scale, with every step shown.

  • 16:9
    Aspect RatioFind, resize or check an image
  • φ
    Golden RatioLong and short segments of 1.618
  • 1:N
    Scale RatioReal size, model size and scale
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Aspect, Golden & Scale Ratio Calculators

Designers, photographers, model makers and architects use three ratios more than any others: aspect ratio, the golden ratio and scale ratio. These free calculators handle all three in one place, and every result comes with a clear step-by-step solution, so you can see exactly how each number was found.

Aspect Ratio Calculator

Aspect ratio is the relationship between width and height, written as W : H. A 1920 × 1080 screen, for example, simplifies to 16 : 9.

How to use it

  1. Choose Find the ratio and enter a width and a height.
  2. Press Calculate to see the simplified ratio, the decimal ratio and the nearest common format, such as 16:9, 4:3 or 21:9.
  3. To resize, choose Resize, enter the original size, then type the new width or the new height. The calculator fills in the other side.
  4. To check a photo, choose Check an image and pick a file. It is read on your device and never uploaded.

Unlike many aspect ratio tools, this one also explains the working: it finds the greatest common divisor, divides both sides by it, and shows how far your size is from the nearest standard ratio.

Golden Ratio Calculator

The golden ratio, φ (phi), is about 1.618. A line is split in the golden ratio when the whole divided by the long part equals the long part divided by the short part.

How to use it

  1. Enter one known value.
  2. Choose whether it is the whole length, the long segment or the short segment.
  3. Press Calculate to get the other two values, a proportion bar and the full working.

For a 100 px layout, the long segment is 61.8 px and the short segment is 38.2 px. Use it for column widths, logo proportions, type scales and photo crops.

Scale Ratio Calculator

A scale ratio such as 1 : 100 means one unit on the model or drawing equals 100 units in real life.

How to use it

  1. Pick a mode: Real → Scaled, Scaled → Real, Find the scale or Change scale.
  2. Enter your length and choose its unit, such as mm, cm, m, inches or feet.
  3. Type the scale number N or pick a preset, such as 1:87 (HO), 1:160 (N) or 1:48.
  4. Press Calculate.

A 12 m building at 1 : 100 becomes a 12 cm model. With Change scale, you can convert a part measured on an HO model straight to N scale, a step many scale calculators skip.

Why use these ratio calculators?

  • Every answer shows its working, not just a number.
  • Unit conversion and common presets are built in.
  • Images are checked in your browser, so nothing is uploaded.
  • An on-screen keypad makes them easy to use on a phone.
  • They are free and need no sign-up.

Frequently asked questions

What is the most common aspect ratio?

16 : 9 is the standard for HD video, TVs, monitors and YouTube. Vertical video for Reels, Shorts and TikTok uses 9 : 16.

How do I calculate the golden ratio of a number?

Divide the number by 1.618 to get the long segment. Subtract that from the number to get the short segment.

What does a 1 : 50 scale mean?

Every 1 cm on the model or drawing represents 50 cm, or 0.5 m, in real life.

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