Range Intersection Calculator
Find addresses shared between ranges.
Range Intersection Calculator: inputs and results
Enter an IP address, CIDR prefix, or range. Then check its first and last address below.
Calculated Boundaries & ParametersReady
Key Capabilities
- •100% Client-Side: Zero telemetry or server latency.
- •RFC Compliant: Exact 32-bit and 128-bit integer precision.
- •Quick Copy: Instant access to CIDR, mask, and range bounds.
- •Cross-Platform: Works on desktop, tablet, and mobile browsers.
Related Subnet Math & Set OperationsAll Tools
Bitwise Subnet Calculator
Show address-and-mask operations.
IP Address Offset Calculator
Add or subtract address positions.
Address Distance Calculator
Count positions between two addresses.
Subnet Boundary Checker
Check alignment to a specified prefix.
IP-in-Range Checker
Test whether an address belongs.
IP-in-Subnet Checker
Test membership within a CIDR block.
How Range Intersection Calculator Works?
This tool works by taking the larger of the 2 start addresses and the smaller of the 2 end addresses. A valid result is the set of addresses both ranges share.
Enter range A
Type
172.16.0.0 – 172.16.3.255.Enter range B
Type
172.16.2.128 – 172.16.6.0.Compute max start and min end
max start =
172.16.2.128, min end =172.16.3.255.Report the intersection
The shared range holds 384 addresses and converts to 2 CIDR blocks.
Range Intersection Calculator Formula
The formula is A ∩ B = [max(S_A, S_B), min(E_A, E_B)], empty when the start exceeds the end.
Intersection start
S = max(S_A, S_B)Later of the 2 starts.
Intersection end
E = min(E_A, E_B)Earlier of the 2 ends.
Empty set
S > ENo shared addresses.
Size
E − S + 1Shared address count.
Worked example: 172.16.0.0–172.16.3.255 ∩ 172.16.2.128–172.16.6.0
Start = max(172.16.0.0, 172.16.2.128) = 172.16.2.128 End = min(172.16.3.255, 172.16.6.0) = 172.16.3.255 Size = 384 CIDR = 172.16.2.128/25, 172.16.3.0/24
Range Intersection Calculator Conversion Table
The table computes the intersection of 7 range pairs, with the size and CIDR form of each result.
| Range A | Range B | Intersection | Size | CIDR Blocks |
|---|---|---|---|---|
| 172.16.0.0 – 172.16.3.255 | 172.16.2.128 – 172.16.6.0 | 172.16.2.128 – 172.16.3.255 | 384 | 172.16.2.128/25, 172.16.3.0/24 |
| 10.0.0.0 – 10.0.0.255 | 10.0.0.200 – 10.0.1.50 | 10.0.0.200 – 10.0.0.255 | 56 | 10.0.0.200/29, 10.0.0.208/28, 10.0.0.224/27 |
| 10.0.0.0 – 10.0.255.255 | 10.0.16.0 – 10.0.31.255 | 10.0.16.0 – 10.0.31.255 | 4,096 | 10.0.16.0/20 |
| 192.168.1.1 – 192.168.1.100 | 192.168.1.50 – 192.168.1.60 | 192.168.1.50 – 192.168.1.60 | 11 | 192.168.1.50/31, 192.168.1.52/30, 192.168.1.56/30, 192.168.1.60/32 |
| 10.1.0.0 – 10.1.0.99 | 10.1.0.100 – 10.1.0.200 | Empty | 0 | — |
| 203.0.113.0 – 203.0.113.127 | 203.0.113.96 – 203.0.113.255 | 203.0.113.96 – 203.0.113.127 | 32 | 203.0.113.96/27 |
| 100.64.0.0 – 100.127.255.255 | 100.100.0.0 – 100.200.0.0 | 100.100.0.0 – 100.127.255.255 | 1,835,008 | 100.100.0.0/14, 100.104.0.0/13, 100.112.0.0/12 |
What is Range Intersection Calculator?
The Range Intersection Calculator is a tool that returns the addresses common to 2 IPv4 ranges.
Intersection answers "which addresses do both lists cover". A firewall rule and a threat feed, a DHCP pool and a static block, or 2 partners' allow-lists all reduce to the same calculation.
The result appears as a range and as exact CIDR blocks, ready for rules that need the shared space only.
What are the uses of Range Intersection Calculator?
There are 4 main uses of the Range Intersection Calculator, including rule scoping, threat matching, and conflict sizing.
Scoping firewall rules
Rules that apply only where 2 policies agree use the intersection.
Matching threat feeds to assets
The intersection of a threat range and owned space shows affected addresses.
Sizing conflicts
The size of a pool–static intersection shows how many addresses are double-assigned.
Comparing provider ranges
Shared space between 2 cloud provider lists points to common infrastructure.