FOV Calculator: Convert Field of View Between Aspect Ratios (2026)

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Convert horizontal and vertical FOV between preset or custom render dimensions, with same-view references for 4:3, 16:9, and ultrawide.

Geometry check: 90° horizontal at 4:3 equals 73.74° vertical and 106.26° horizontal at 16:9.

Source angle

Use the ratio that the entered FOV describes. It can differ from the monitor's physical ratio.

Target render

This calculator uses a Hor+ model: it keeps vertical FOV fixed and solves for horizontal FOV at the target ratio. Check the destination's FOV axis and reference ratio before using the number.
-° horizontal
Source
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Target
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The calculator cannot identify a game's slider convention. A mismatch can come from the axis, a fixed reference ratio, another aspect-ratio constraint, or a limit on accepted values. Use the source ratio and axis documented by the software.

This calculator converts horizontal and vertical field of view between two aspect ratios. Choose preset ratios or enter exact source and target render dimensions. The result keeps the vertical angle fixed and recalculates the horizontal angle for the target.

Treat the source ratio as the reference ratio for the FOV value you entered. That reference can differ from the physical monitor. If software defines its slider against a fixed base ratio, use that base as the source and use the actual render dimensions as the target.

Custom dimensions matter for ultrawide output. A 2560x1080 frame is 2.37037:1; a 3440x1440 frame is 2.38889:1. The reference table keeps them separate and shows each horizontal angle for the same vertical view.

How the conversion works

Horizontal and vertical FOV are linked by the frame’s aspect ratio:

vertical = 2 × atan(tan(horizontal ÷ 2) ÷ aspect ratio)

horizontal = 2 × atan(tan(vertical ÷ 2) × aspect ratio)

Unity documents the same inputs and outputs in its official HorizontalToVerticalFieldOfView and VerticalToHorizontalFieldOfView APIs: an angle in degrees plus an aspect ratio. I keep the resulting vertical angle constant when converting to the target ratio and when building the reference table. That is the Hor+ model used by this tool. It is a calculation choice, not a claim that every game uses that behavior. Epic’s official EAspectRatioAxisConstraint reference lists separate constraints for maintaining horizontal FOV, vertical FOV, or the major axis.

Reading the result

The headline is the target horizontal angle. The source and target cards show both axes, while the table expresses the same vertical angle at 4:3, 16:9, 2560x1080, and 3440x1440.

Use the horizontal figure only when the destination expects horizontal FOV. Use the vertical figure when it expects vertical FOV. If the software uses another reference ratio or rejects the angle, consult its own settings documentation rather than changing the geometry to force a match.

The share link includes the entered FOV and axis, plus presets and any active custom dimensions.

Calculations stay in the browser.

To identify a display ratio from dimensions, use the Aspect Ratio Calculator. The Monitor Size Calculator handles physical width, height, and pixel density; those measurements are separate from the angular conversion here.

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Frequently asked questions

What does an FOV number measure?
A field-of-view number is an angle in degrees. Horizontal FOV measures the visible angle across the width of a frame, while vertical FOV measures it across the height. The axis and reference aspect ratio are required to interpret the number.
Why does the source ratio matter?
The source ratio tells the calculator which frame shape the entered angle describes. It is a reference for the angle, and it may differ from the monitor’s physical ratio when software defines its slider against a fixed base ratio.
What do custom render dimensions change?
Custom width and height set the exact aspect ratio used in the conversion. The calculator divides width by height, so 2560x1080 and 3440x1440 remain distinct even though both are commonly grouped under the same ultrawide label.
What does Hor+ mean in this calculator?
The Hor+ model keeps vertical FOV constant and calculates a new horizontal FOV for the target aspect ratio. It describes this calculator’s conversion rule; it does not establish which axis or scaling rule a particular game uses.
Why can the converted angle differ from a game’s slider?
A game may label its slider on another axis, use a fixed reference ratio, constrain the field of view by a different axis, or cap the accepted range. Check the game’s own documentation before treating a converted angle as a slider value.