Redimensiona cualquier ancho / alto manteniendo la relación de aspecto, con preajustes de un clic para cada red social y estándar de cine, de 1:1 a 21:9.
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Proporción = ancho original ÷ alto original. Al bloquear el ancho, el nuevo alto = nuevo ancho ÷ proporción. Al bloquear el alto: nuevo ancho = nuevo alto × proporción.
El modo "Calcular proporción" reduce ancho:alto a su forma entera más simple usando el máximo común divisor.
Two modes share one underlying calculation. Ratio = original width ÷ original height, and the Calculate ratio from dimensions mode reduces that to its simplest integer form using the greatest common divisor, turning 1920 × 1080 into 16:9. Resize keeping ratio applies it instead: with Lock width, new height = new width ÷ ratio; with Lock height, new width = new height × ratio. The other field updates as you type, and a dashed preview box redraws to the resulting shape.
The Lock dropdown decides which field you drive, though the tool also tracks whichever of the two new-dimension fields you edited last and follows that. The eight presets — 1:1 square, 4:3, 16:9 HD, 21:9 ultrawide, 9:16 vertical, 4:5 IG portrait, 1.91:1 FB / link and 2:3 Pinterest — work by keeping your original width and rewriting the original height to match the chosen ratio, then copying both values into the new fields.
The results are purely geometric: you get the dimensions that preserve proportion, not guidance on how to crop or letterbox an image that is already the wrong shape. Displayed values are rounded, so a ratio such as 21:9 can land half a pixel off and produce a one-pixel discrepancy in real output. Non-integer original dimensions are rounded before the greatest common divisor runs, which makes the simplified ratio approximate for those.
720 tall. With Lock width selected, type 1280 into New width and the height fills in automatically from the 16:9 ratio. The scale factor rows underneath confirm that both dimensions changed by the same 0.6667 multiplier, which is what preserving proportion means.
Switch Mode to Calculate ratio from dimensions and enter the original width and height. The headline gives the simplest whole-number form, and the decimal ratio row beneath it shows six decimal places, which helps when the ratio does not reduce to anything tidy.
Use the 1.91:1 FB / link preset, stored internally as 191:100. Click it and the original height recalculates from your current width, so a 1920-wide image becomes 1920 × 1005. Instagram portrait has its own separate 4:5 preset button.
Presets set the ratio by keeping the original width you entered and recomputing the original height from it, then copying both into the new-dimension fields. If you need to preserve a source image's true dimensions, type your target into the new width or height field instead.
It resizes proportionally only, with no crop, letterbox or fit-and-fill logic. If your source is 16:9 and you need 9:16, the calculator hands you a correctly proportioned box, but you still decide in an image editor which content gets cut away.
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