16 BIT KNX Group Address Utility

KNX Group Address Calculator

Use this KNX Group Address Calculator to convert 3-level KNX group addresses such as 1/2/10, 2-level addresses such as 1/522, and raw 16-bit hexadecimal or decimal group-address values.

✓ 3-Level Address ✓ 2-Level Address ✓ Hex Converter ✓ Decimal Converter ✓ 16-Bit Decoder

KNX

Encode / Decode Group Address

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Main Group 5-bit main-group field: 0–31.

Middle Group 3-bit middle-group field: 0–7.

Sub Group 8-bit subgroup field: 0–255.

Address structure: In 3-level notation, the 16-bit value is split into 5-bit Main / 3-bit Middle / 8-bit Sub. In 2-level notation, the same 16 bits are interpreted as 5-bit Main / 11-bit Sub.

KNX Group Address Result Converted

Raw 16-Bit Group Address –

3-Level Address –

2-Level Address –

Hex Value –

Decimal Value –

High Byte –

Low Byte –

Binary –

Address Width 16 bits

3-Level Bit Layout

Main — 5 bits –

Middle — 3 bits –

Sub — 8 bits –

Bit-Level Calculation

Raw Group Address

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What Is a KNX Group Address Calculator?

A KNX Group Address Calculator converts the hierarchical group-address notation used in KNX engineering projects into the underlying 16-bit numerical address. It can also decode a raw hexadecimal or decimal value back into its group address components.

KNX group addresses are used for communication between group objects rather than for identifying an individual physical device. The hierarchy shown in engineering software is a convenient interpretation of the same 16-bit group address.

KNX 3-Level Group Address Format

The commonly used three-level representation has the form:

Main / Middle / Sub with: Main = 5 bits = 0–31 Middle = 3 bits = 0–7 Sub = 8 bits = 0–255

An example group address is 1/2/10.

KNX 3-Level Address Formula

For: Main = M Middle = G Sub = S the packed 16-bit address is: Address = (M << 11) | (G << 8) | S Equivalent arithmetic: Address = Main × 2048 + Middle × 256 + Sub

Example: Convert KNX 1/2/10

Main: 1 × 2048 = 2048 = 0x0800 Middle: 2 × 256 = 512 = 0x0200 Sub: 10 = 0x000A Combined: 0x0800 + 0x0200 + 0x000A = 0x0A0A Decimal: 2570

KNX 2-Level Group Address Format

A two-level KNX address uses a five-bit main group and an eleven-bit subgroup.

Main / Sub Main = 5 bits Sub = 11 bits Ranges: Main = 0–31 Sub = 0–2047

KNX 2-Level Address Formula

Address = (Main << 11) | Sub or: Address = Main × 2048 + Sub

3-Level and 2-Level Addresses Can Represent the Same Value

The two hierarchies are different ways to display the same 16-bit address. For example:

Three-level: 1/2/10 Raw: 0x0A0A The lower eleven bits equal: (2 × 256) + 10 = 522 Therefore the two-level form is: 1/522

Both notations correspond to the same numerical group address.

KNX Group Address Bit Layout

Format	Field	Bits	Range
3-Level	Main Group	5	0–31
3-Level	Middle Group	3	0–7
3-Level	Sub Group	8	0–255
2-Level	Main Group	5	0–31
2-Level	Sub Group	11	0–2047

How to Decode a Raw KNX Group Address

For 3-level interpretation, extract each field from the 16-bit value.

Main = (Address >> 11) & 0x1F Middle = (Address >> 8) & 0x07 Sub = Address & 0xFF

For two-level notation:

Main = (Address >> 11) & 0x1F Sub = Address & 0x07FF

Example: Decode 0x0A0A

Raw: 0x0A0A 3-Level: Main = 0x0A0A >> 11 = 1 Middle = (0x0A0A >> 8) & 7 = 2 Sub = 0x0A0A & 0xFF = 10 Result: 1/2/10 2-Level: 1/522

KNX Group Address Decimal and Hexadecimal

The hierarchical notation is ultimately backed by a 16-bit numeric value. The same address may therefore be displayed in several equivalent forms.

3-Level: 1/2/10 2-Level: 1/522 Hex: 0x0A0A Decimal: 2570 Binary: 0000101000001010

KNX Group Address Range

Because the group-address field is 16 bits wide, the raw numeric range is:

Minimum: 0x0000 = 0 decimal Maximum: 0xFFFF = 65535 decimal

In 3-level notation this maximum bit pattern decodes as:

31/7/255

and in 2-level notation:

31/2047

KNX Group Address vs Individual Address

Group Address

Used for group communication between communication objects. It represents a functional communication destination rather than one particular physical device.

Individual Address

Identifies an individual KNX device using area, line and device addressing. It serves a different purpose from a group address.

Do not use this calculator to convert KNX individual addresses such as 1.1.10. This page is specifically for KNX group addresses.

KNX Main, Middle and Sub Groups

In a three-level structure, project designers can organize group addresses into a logical hierarchy.

Example: 1 / 2 / 10 could conceptually be organized as: Main: Lighting Middle: Ground Floor Sub: Kitchen Ceiling

Those labels are project-specific. The actual bus address is the numeric 16-bit value produced by the hierarchy.

Why Convert KNX Group Addresses to Hex?

Hexadecimal representation is useful when inspecting low-level telegrams, debugging gateways, comparing configuration data or working with software that stores group addresses as raw numerical fields.

For example, recognizing that 1/2/10 equals 0x0A0A can help connect the human project hierarchy with the raw address visible in another protocol or diagnostic interface.

KNX Group Address Byte Order

A raw 16-bit group address can be split into a high byte and low byte.

For: 0x0A0A the bytes are: High Byte = 0x0A Low Byte = 0x0A

The calculator displays these separately for protocol analysis and debugging.

Common KNX Group Address Mistakes

Using Middle Group Above 7

The three-level middle group occupies only three bits, so its valid range is 0–7.

Using Subgroup Above 255

The three-level subgroup occupies eight bits and therefore ranges from 0–255.

Mixing 2-Level and 3-Level Formats

The subgroup ranges differ because the underlying 11 bits are divided differently.

Confusing Group and Individual Addresses

Group addresses and KNX device individual addresses have different purposes and layouts.

Assuming Hierarchy Changes Raw Value

Two-level and three-level notation can describe the same underlying 16-bit address.

Reading Decimal as Hexadecimal

Decimal 2570 and hexadecimal 0x0A0A represent the same address but use different number bases.

KNX Group Address Calculator FAQs

What is a KNX group address?

A KNX group address is a 16-bit communication destination used by KNX group objects for functional communication.

How many bits are in a KNX group address?

The raw KNX group address is 16 bits wide.

What is the KNX 3-level format?

Three-level notation uses Main Group / Middle Group / Sub Group with 5, 3 and 8 bits respectively.

What is the range of KNX main group?

The five-bit main group ranges from 0 through 31.

What is the range of KNX middle group?

The three-bit middle group ranges from 0 through 7.

What is the range of a 3-level KNX subgroup?

The eight-bit subgroup ranges from 0 through 255.

What is the KNX 2-level format?

Two-level notation uses a five-bit Main Group and eleven-bit Sub Group.

What is the range of a 2-level subgroup?

The eleven-bit subgroup ranges from 0 through 2047.

What is KNX 1/2/10 in hexadecimal?

1/2/10 encodes to hexadecimal 0x0A0A.

What is KNX 1/2/10 in decimal?

The raw 16-bit decimal value is 2570.

What is the 2-level equivalent of 1/2/10?

The two-level representation is 1/522 because the middle and sub fields form the lower 11 bits.

How do I calculate a 3-level KNX address?

Multiply Main by 2048, Middle by 256, add the Sub value and combine the result as a 16-bit address.

How do I decode a raw KNX group address?

For three-level notation, extract bits 15–11 as Main, bits 10–8 as Middle and bits 7–0 as Sub.

What is the maximum raw KNX group address?

The maximum 16-bit value is 0xFFFF, or 65535 decimal.

What does 0xFFFF decode to in 3-level KNX notation?

It decodes to 31/7/255.

What does 0xFFFF decode to in 2-level notation?

It decodes to 31/2047.

Is a KNX group address the same as an individual address?

No. A group address identifies a communication destination. An individual address identifies a specific KNX device.

Can the same raw address have both 2-level and 3-level notation?

Yes. They are alternative hierarchical interpretations of the same 16-bit group-address value.

Convert KNX 3-Level, 2-Level and Raw Group Addresses

Enter a KNX hierarchy to calculate its hexadecimal, decimal, binary and byte representation, or decode a raw 16-bit group address into both 3-level and 2-level notation.