# vkGetPhysicalDeviceDescriptorSizeEXT(3) Manual Page

## Name

vkGetPhysicalDeviceDescriptorSizeEXT - Report specific descriptor sizes for each descriptor type

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## C Specification

To query the size of heap descriptor for a specific VkDescriptorType, call:

    // Provided by VK_EXT_descriptor_heap
    VkDeviceSize vkGetPhysicalDeviceDescriptorSizeEXT(
        VkPhysicalDevice                            physicalDevice,
        VkDescriptorType                            descriptorType);

## Parameters

- `physicalDevice` is the physical device from which to query the descriptor sizes.

- `descriptorType` is a VkDescriptorType specifying the type of heap descriptor to query the size for.

## Description

The return value of this function will be a VkDeviceSize indicating the size in bytes (N) of a heap descriptor with a type equal to `descriptorType`. When a descriptor of this type is written by vkWriteResourceDescriptorsEXT or vkWriteSamplerDescriptorsEXT, only the first N bytes are written; the rest will not be accessed and can be safely discarded when copying descriptors around. Additionally, those first N bytes are the only bytes that will be accessed when the descriptor is accessed in the shader. N will never be larger than the applicable limits in VkPhysicalDeviceDescriptorHeapTensorPropertiesARM or VkPhysicalDeviceDescriptorHeapPropertiesEXT.

Note | Values returned by this function have other requirements, so for example may not be power-of-two values.

Note | This command is not intended for general use, and is for tools that already take advantage of tighter packing with other similar features (e.g. `VK_EXT_descriptor_buffer`) to optimize accesses in some cases. Applications can safely ignore this function and are advised to do so, to avoid depending on non-portable packing.

Valid Usage

- VUID-vkGetPhysicalDeviceDescriptorSizeEXT-type-11362
  `type` must be one of VK_DESCRIPTOR_TYPE_SAMPLER, VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER, VK_DESCRIPTOR_TYPE_STORAGE_BUFFER, VK_DESCRIPTOR_TYPE_SAMPLED_IMAGE, VK_DESCRIPTOR_TYPE_STORAGE_IMAGE, VK_DESCRIPTOR_TYPE_UNIFORM_TEXEL_BUFFER, VK_DESCRIPTOR_TYPE_STORAGE_TEXEL_BUFFER, VK_DESCRIPTOR_TYPE_SAMPLE_WEIGHT_IMAGE_QCOM, VK_DESCRIPTOR_TYPE_BLOCK_MATCH_IMAGE_QCOM, VK_DESCRIPTOR_TYPE_ACCELERATION_STRUCTURE_KHR, VK_DESCRIPTOR_TYPE_ACCELERATION_STRUCTURE_NV, VK_DESCRIPTOR_TYPE_PARTITIONED_ACCELERATION_STRUCTURE_NV, VK_DESCRIPTOR_TYPE_TENSOR_ARM, or VK_DESCRIPTOR_TYPE_INPUT_ATTACHMENT

Valid Usage (Implicit)

- VUID-vkGetPhysicalDeviceDescriptorSizeEXT-physicalDevice-parameter
  `physicalDevice` must be a valid VkPhysicalDevice handle

- VUID-vkGetPhysicalDeviceDescriptorSizeEXT-descriptorType-parameter
  `descriptorType` must be a valid VkDescriptorType value

## See Also

VK_EXT_descriptor_heap, VkDescriptorType, VkPhysicalDevice

## Document Notes

For more information, see the Vulkan Specification.

This page is extracted from the Vulkan Specification. Fixes and changes should be made to the Specification, not directly.

## Copyright

Copyright 2014-2026 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0