Free calculator
Aspect Ratio Calculator
2.39:1 inside 1920 × 1080 is 1920 × 804, with 138 px letterbox bars top and bottom. Pick any source and ratio to get the largest frame that fits, the bars in pixels, an anamorphic desqueeze, or the picture scaled to a delivery size.
Free, no sign-up. Runs in your browser.
This web tool keeps Smart-rounded frames inside the source, snaps a typed ratio to the nearest standard, and scales the cropped frame to a delivery size. Save, share and get the Pro tools in the app.
How it works
if W ÷ r ≤ H: frame = W × (W ÷ r), else frame = (H × r) × HA ratio wider than the source keeps the full width and loses height (letterbox); a narrower ratio keeps the full height and loses width (pillarbox). 2.39:1 is worked out as 4096 ÷ 1716 = 2.387, the shape of the 4096 × 1716 scope frame, 16:9 as exactly 16 ÷ 9, 1.33:1 as 4:3 and 1.66:1 as 5:3. A vertical ratio such as 9:16 is worked out with the camera turned 90°.
Where
- W, H
- source width and height(px)
- r
- target ratio, width ÷ height (2.39 for 2.39:1)
top = bottom = (H − h) ÷ 2; left = right = (W − w) ÷ 2The picture sits in the middle, so the space left over splits into two equal bars. w and h are the frame size after rounding.
Smart: a standard size within 0.5%, else 2 × round(x ÷ 2)Smart rounding (the default) snaps a dimension to a common video size such as 1080, 2160 or 1716 when it is within 0.5%, and otherwise to the nearest even pixel, which encoders prefer; the other side is then worked out from the rounded one. A Smart frame never ends up bigger than the source. Exact keeps the fraction (804.38) so you can see the true size.
desqueezed width = W × squeeze; fit scale = min(TW ÷ (W × squeeze), TH ÷ H)An anamorphic lens squeezes the picture sideways; desqueezing multiplies the width by the squeeze factor. To fit the desqueezed picture inside a target size (TW × TH), both sides are multiplied by the smaller of the two scales.
Anamorphic footage
Choose a lens squeeze to desqueeze anamorphic footage. A 2880 × 2160 recording shot with a 2× anamorphic lens desqueezes to 5760 × 2160, a 2.67:1 picture. Fit to target then scales that picture into a delivery frame: inside 3840 × 2160 it becomes 3840 × 1440, with 360 px bars top and bottom.
Scaling to a delivery size
Turn on Scale to a delivery size to place the frame in another resolution. Fit shows the whole picture and adds bars, Fill covers the delivery frame and cuts off the overflow, and Stretch fills it by scaling each axis differently, which distorts the image. The DCI 4K 2.39:1 frame, 4096 × 1716, fit into 1920 × 1080 is 1920 × 804 with 138 px bars.
Worked example
2.39:1 inside a 1920 × 1080 frame
- 2.39:1 is worked out as 4096 ÷ 1716 = 2.38695
- 1920 ÷ 1080 = 1.778, narrower than 2.387, so the width is kept: w = 1920
- h = 1920 ÷ 2.38695 = 804.375
- Smart rounding to the nearest even pixel: 804.375 → 804
- Bars: (1080 − 804) ÷ 2 = 138 px top and bottom
2.39:1 in 1920 × 1080 is 1920 × 804, with 138 px bars top and bottom
Quick reference
Common ratios inside 1920 × 1080 and 3840 × 2160 (Smart rounding, bars in pixels on each side)
| Ratio | In 1920 × 1080 | Bars (HD) | In 3840 × 2160 | Bars (UHD) |
|---|---|---|---|---|
| 4:3 (1.33:1) | 1440 × 1080 | 240 left and right | 2880 × 2160 | 480 left and right |
| 1.66:1 | 1800 × 1080 | 60 left and right | 3600 × 2160 | 120 left and right |
| 16:9 (1.78:1) | 1920 × 1080 | None | 3840 × 2160 | None |
| 1.85:1 | 1920 × 1038 | 21 top and bottom | 3840 × 2076 | 42 top and bottom |
| 2:1 | 1920 × 960 | 60 top and bottom | 3840 × 1920 | 120 top and bottom |
| 21:9 (2.33:1) | 1920 × 822 | 129 top and bottom | 3840 × 1646 | 257 top and bottom |
| 2.35:1 | 1920 × 818 | 131 top and bottom | 3840 × 1634 | 263 top and bottom |
| 2.39:1 | 1920 × 804 | 138 top and bottom | 3840 × 1608 | 276 top and bottom |
| 2.76:1 | 1920 × 696 | 192 top and bottom | 3840 × 1392 | 384 top and bottom |
| 1:1 | 1080 × 1080 | 420 left and right | 2160 × 2160 | 840 left and right |
Save, share and get the Pro tools in the CineMath app
CineMath is a free download for iPhone, iPad and Mac, with this calculator built in. In version 1.3, coming soon to the App Store, CineMath Professional saves calculations to your history, shares them as links, and adds the Camera Database and Data Planning.
Questions
What resolution is 2.39:1 in 4K?
In 4K UHD (3840 × 2160) a 2.39:1 frame is 3840 × 1608, with 276 px bars top and bottom (the exact height is 1608.75). In DCI 4K (4096 × 2160) it is 4096 × 1716, the 2.39:1 frame SMPTE ST 428-1 gives for a 4K cinema image, with 222 px bars.
How big are the letterbox bars for 2.39:1 in 1080p?
138 px top and bottom. 1920 ÷ 2.387 = 804.375, which rounds to an 804 px tall picture, and (1080 − 804) ÷ 2 = 138. If you letterbox to 1920 × 800 instead, the bars are 140 px and the frame is 2.40:1.
What is the difference between 1.85:1 and 2.39:1?
They are the two common theatrical shapes, often called flat (1.85:1) and scope (2.39:1). Inside a DCI 4K container, SMPTE ST 428-1 gives 3996 × 2160 for 1.85:1, which keeps the full height, and 4096 × 1716 for 2.39:1, which keeps the full width. In a 1920 × 1080 frame, 1.85:1 is 1920 × 1038 with 21 px bars and 2.39:1 is 1920 × 804 with 138 px bars.
What is 21:9 in pixels?
21:9 is 2.333:1. Inside 1920 × 1080 it is 1920 × 822 (822.86 exactly) with 129 px bars, and inside 3840 × 2160 it is 3840 × 1646 with 257 px bars. Choose Custom ratio and type 21:9 to work it out for any source.
How do I calculate a frame size for an aspect ratio?
Divide the source width by the ratio. If the answer fits inside the source height, that is the height of the frame and the width stays the same. If not, multiply the source height by the ratio to get the width instead. For 1.85:1 in 3840 × 2160: 3840 ÷ 1.85 = 2075.7, which fits, so the frame is 3840 × 2076 after rounding to an even pixel.
Should I use Smart or Exact rounding?
Use Smart for a frame you will make: it gives whole, even pixel sizes and snaps to a standard size such as 1716 or 2160 when it is within 0.5%, and it never goes past the edge of the source. Use Exact to see the true value, such as 804.375 for 2.39:1 in 1080p, before any rounding.