Free Film & Video Tool · Calculator
Aspect Ratio & Resolution Calculator
Work out pixel dimensions for any target aspect ratio — compare crop-to-fill with fit-with-bars, see exactly how many pixels are cropped or padded, and scale to a delivery size.
Deterministic maths that runs entirely in your browser — no AI model, no uploads, no account. Formulas and assumptions are explained below the calculator.
Inputs
Results update as you type.
Pick a preset or type your own, e.g. 16:9, 2.39:1 or 1.85.
Scale the result to a final frame width — height is set by the target ratio.
Results
Source 1,920 × 1,080 (16:9 (1.78:1)) → target 1:1.78.
Crop to fill
608 × 1,080
- Left / right removed: 656 px each
- Top / bottom removed: 0 px each
- Image kept: 31.7%
Fills the whole frame; you lose the edges outside the highlighted area.
Fit with bars
1,920 × 3,414
- Bars: letterbox, 1,167 px each top/bottom
- Picture covers: 31.6% of the frame
Keeps every pixel of the source; the rest of the frame is filled with bars (or a background).
How it works
Aspect ratio is a frame's width divided by its height. When a source and its destination have different ratios, there are only two ways to avoid stretching the picture: crop to fill (keep the largest target-shaped area inside the source and discard the edges) or fit with bars (place the whole source on a target-shaped canvas and fill the gaps with letterbox or pillarbox bars). This calculator works out both, so you can see exactly what each approach costs.
It calculates dimensions only — it doesn't open, transcode or resize video files.
The formulas
- Crop to fill: if the target is wider than the source, keep the full width and set height = width ÷ ratio; otherwise keep the full height and set width = height × ratio.
- Fit with bars: if the target is wider than the source, keep the full height and widen the canvas to height × ratio (pillarbox); otherwise keep the full width and heighten the canvas to width ÷ ratio (letterbox).
- Delivery size: delivery height = delivery width ÷ ratio. Crop scales the source by the larger of the two width/height scale factors; fit scales by the smaller.
- Crop amounts and bars are split equally between opposite sides (any odd pixel goes to the right or bottom).
Worked examples
| Source → target | Method | Result | What changes |
|---|---|---|---|
| 1920 × 1080 → 9:16 | Crop to fill | 608 × 1080 | 656 px removed from each side; 31.7% of the image kept |
| 1920 × 1080 → 2.39:1 | Crop to fill | 1920 × 804 | 138 px removed from top and bottom |
| 1920 × 1080 → 4:3 | Fit with bars | 1920 × 1440 | 180 px letterbox bars top and bottom |
| 3840 × 2160 → 9:16 at 1080 wide | Crop to fill | 1080 × 1920 | Uses a 1215 × 2160 slice of the UHD frame, scaled down — no upscaling |
Letterbox inside 16:9 vs a true scope frame
“Fit with bars” to 2.39:1 from a 16:9 source adds bars at the sides, because the scope canvas is wider than the source. The familiar look of black bars above and below a widescreen film on a 16:9 screen is the opposite case: a 2.39:1 picture fitted inside a 16:9 frame. To mimic it from 16:9 footage, crop to 2.39:1 and then fit that result back into 16:9. Read more in our guide to letterboxing in film.
Assumptions and limitations
- Square pixels are assumed. Anamorphic or non-square-pixel formats need their pixel aspect ratio applied first.
- Crops are centred. Real reframes often shift the crop to follow the subject — the crop size stays the same.
- Pixel values are rounded to whole (or even) numbers, so the resulting ratio can differ from the target by a fraction of a pixel.
- Platform safe zones and recommended upload sizes change over time and aren't built in — check current platform guidance.
FAQ
- Does this tool resize or convert my video file?
- No. It calculates dimensions, crop amounts and bar sizes only. Use the numbers in your editing software or encoder to make the actual change.
- Should I crop or add bars?
- Crop to fill when the important action sits near the centre and you want a full-frame result. Fit with bars when nothing at the edges can be lost — titles, wide compositions, or archive material.
- Why round to even numbers?
- Common delivery codecs using 4:2:0 chroma subsampling (such as most H.264 and H.265 exports) need even widths and heights. Leave the option on unless you know your format allows odd dimensions.
- Where are the platform presets?
- We list ratios rather than named platform specs, because platforms change their recommended sizes and safe zones without notice. Check the platform's current upload guidance, then enter its ratio and width here.
- Is it free to use?
- Yes. There's no signup or account, and the calculations run entirely in your browser — nothing you type is sent to a server or an AI model.
- Can I share or save my results?
- Yes. Your inputs are saved in the page address as you type, so “Copy link” gives you a URL that reopens the calculator with the same settings. “Copy results” copies a plain-text summary.
Further reading
- What Is Aspect Ratio? Definition With Examples From Films
- What Is 16:9 Aspect Ratio? Why Is Widescreen So Popular
- What is 4:3 Aspect Ratio? Definition & Examples
- What Is Anamorphic Widescreen?
- What Is Letterboxing in Film?
- The Growing Use of Vertical Videos in Social Media
- What Is 4K Resolution in Filmmaking?
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