What is the difference between crop-to-fill and letterbox-to-fit?

Crop-to-fill (cover) scales the source so it completely fills the target ratio, then trims the overflowing edges, so no bars appear but some pixels are discarded. Letterbox-to-fit (contain) scales the source so the whole frame is visible inside a target-ratio canvas, adding bars to pad the empty space, so nothing is lost but the picture no longer fills the screen.

How are the cropped dimensions calculated?

The tool compares the source ratio (width divided by height) with the target ratio. If the source is wider than the target it keeps the full height and crops the sides to height times target ratio; if the source is taller it keeps the full width and crops the top and bottom to width divided by target ratio. Both outputs match the exact target aspect ratio.

When do I get letterbox bars versus pillarbox bars?

You get letterbox bars (top and bottom) when your source is wider than the target ratio, for example fitting a 16:9 clip into a 1:1 square. You get pillarbox bars (left and right) when your source is narrower than the target, such as fitting a vertical 9:16 clip into a 16:9 frame.

How is the storage estimate worked out?

It multiplies the cropped pixel area by a bytes-per-pixel figure for your chosen format (JPEG, WebP, PNG or raw RGBA), then by the number of assets to get total bytes. Dividing by 1024 cubed gives gigabytes, which is multiplied by your price per GB per month for a rough monthly storage cost. Real compressed sizes vary with content, so treat it as a planning estimate.

Does cropping reduce image quality?

Cropping itself does not blur pixels, but it removes part of the frame, so the kept region is what fills the new ratio. The area-kept percentage tells you how much of the original survives. If you crop a 16:9 image to 9:16 you keep only the central strip, so you lose a large share of the width and may need to reframe the subject.

Is my image or data sent anywhere?

No. This calculator only works with the numbers you type. Everything is computed locally in your browser using plain arithmetic, and no resolution, file or value is ever uploaded to a server.

Aspect Ratio Crop & Letterbox Calculator

The Aspect Ratio Crop & Letterbox Calculator turns one resolution into another aspect ratio and shows you exactly what it costs in pixels. Give it a source size and a target ratio and it returns two complete plans: a crop-to-fill that trims the frame so it fills the new ratio edge to edge, and a letterbox-to-fit that keeps every pixel by adding bars. It is built for video editors retargeting a 16:9 master to 9:16 Reels, photographers fitting a 3:2 DSLR shot into a 4:5 Instagram portrait, and developers generating thumbnail variants who need to know how much of each frame survives and how much disk a whole batch will eat.

How it works

Every aspect ratio is just width divided by height. The tool reduces your source resolution and your target ratio to decimals and compares them. When the source is wider than the target, a fill crop keeps the full height and trims the sides; when the source is taller, it keeps the full width and trims the top and bottom. The cropped output always lands on the exact target ratio, and the tool reports how many pixels you cut from each edge, the percentage of frame area you keep, and the raw pixel count discarded.

The letterbox plan does the opposite. Instead of cropping, it grows a target-ratio canvas around your untouched source, so a wide source gains top-and-bottom letterbox bars and a narrow source gains left-and-right pillarbox bars. You see the padded canvas size, the bar thickness on each side, and what share of that canvas the real picture fills.

The storage estimate multiplies the cropped pixel area by a bytes-per-pixel figure for your output format, then by the number of assets, to project total size and a monthly storage bill at your chosen price per GB. Pick JPEG, WebP, PNG-24 or raw RGBA, or type your own measured bytes-per-pixel for a tighter number.

Worked example

Take a 4K UHD master at 3840 x 2160 (16:9) and retarget it to 9:16 vertical for a short-form clip. The source is far wider than 9:16, so a fill crop keeps the full height of 2160 and trims the width down to 2160 x 9 / 16, giving a crop of about 1215 x 2160. That keeps only around 31.6% of the original frame area, trimming roughly 1313 pixels off each side, which is why vertical reframing usually needs the subject re-centred.

If you would rather keep the whole shot, the letterbox plan pads the 3840 width up to a 3840 x 6827 canvas, adding tall pillarbox bars of about 2334 pixels on each side so the landscape picture floats in the middle of a portrait frame. For a batch of 1000 cropped JPEGs at roughly 0.30 bytes per pixel, the tool estimates about 790 MB total and a few US cents per month at typical object-storage pricing.

Formula reference

For a source Ws x Hs and a target ratio Rt = Wt / Ht, the crop-to-fill output is Wc = Hs x Rt, Hc = Hs when Ws/Hs > Rt, otherwise Wc = Ws, Hc = Ws / Rt. Area kept is (Wc x Hc) / (Ws x Hs). The letterbox canvas is the mirror image: a wider source pads to Ws x (Ws / Rt) and a narrower source pads to (Hs x Rt) x Hs. Storage is area x bytesPerPixel x assets, converted to GB by dividing by 1024^3.

Every figure is calculated in your browser from the numbers you enter, and nothing is uploaded or stored.