[{"data":1,"prerenderedAt":213},["ShallowReactive",2],{"page-en-root-tools/subnet-calculator":3},{"content":4,"isFallback":174,"alternates":212},{"id":5,"title":6,"body":7,"description":172,"extension":173,"heroDark":174,"keywords":175,"locale":176,"meta":177,"navigation":204,"path":205,"seo":206,"sitemap":207,"stem":209,"translationKey":210,"__hash__":211},"content/tools/subnet-calculator.md","CIDR & Subnet Calculator — IP Range, Mask, Overlaps",{"type":8,"value":9,"toc":169},"minimark",[10,15,18,26,157,163],[11,12],"essential-hero3-section",{"description":13,"title":14},"CIDR to IP range, and a range back to the CIDR blocks that cover it. Network, usable host range, broadcast, mask and wildcard for IPv4 and IPv6. Split a block into subnets, or paste your whole IP plan and see where it overlaps itself.","Free \u003Cspan class=\"kw-swipe-d\">subnet calculator\u003C/span>",[16,17],"tools-subnet-calculator",{},[19,20],"essential-call-to-action-section",{":primaryButton":21,"subtitle":22,"title":23,"className":24},"{\"text\":\"Get Free Asset Management\",\"url\":\"/free-asset-tracking\"}","A subnet is where a device lives. UNIO24 records what the device is, who signed for it, when its warranty ends, and where it went last. Free IT asset management for unlimited users — no expiring trial.","The plan is documented. Is the hardware?",[25],"cta-tight-bottom",[27,28,29],"essential-content-section",{},[30,31,33,42,45,50,53,60,67,82,86,93,105,112,115,119,125,128,132,135,144],"template",{"v-slot:description":32},"",[34,35,36,37,41],"p",{},"Type ",[38,39,40],"code",{},"10.0.0.4/31"," into most subnet calculators and they will tell you it has zero usable hosts. That answer is twenty years out of date. RFC 3021 made both addresses on a /31 usable precisely so router-to-router links stop wasting two addresses each, and there are probably a few dozen /31s in your network right now carrying traffic that the calculator says cannot exist. This one reports two.",[34,43,44],{},"We sell asset-tracking software, so read the pitch above with a raised eyebrow. The calculator has nothing to do with it — it is arithmetic in your browser.",[46,47,49],"h3",{"id":48},"where-the-plan-check-earns-its-keep","Where the plan check earns its keep",[34,51,52],{},"The single-address mode is table stakes; every tool on this page of results does it. The third tab is the one worth your time.",[34,54,55,56,59],{},"Paste your IP plan — the spreadsheet, the wiki table, the output of whatever your team keeps VLANs in — and every block gets checked against every other block, not just the one above it. That ordering matters more than it sounds. Somebody adds ",[38,57,58],{},"10.0.0.0/16"," at the bottom of the sheet as a \"site summary\" six months after the /24s were carved, and a check that only compares neighbours sails straight past it. Here it lights up against all of them.",[34,61,62,63,66],{},"Column order does not matter either. Feed it ",[38,64,65],{},"VLAN 30, 10.0.30.0/24, printers"," or the other way round; whatever on the line is not a network becomes the label, and the label survives into the CSV so the export still says which row was the printers.",[34,68,69,70,73,74,77,78,81],{},"The output also names the range each block sits in. Private per RFC 1918, obviously, but also carrier-grade NAT (",[38,71,72],{},"100.64.0.0/10","), APIPA link-local (",[38,75,76],{},"169.254.0.0/16","), documentation ranges, and multicast. Finding ",[38,79,80],{},"169.254"," in a plan usually means somebody wrote down what a machine picked up when DHCP failed.",[46,83,85],{"id":84},"cidr-to-range-and-range-back-to-cidr","CIDR to range, and range back to CIDR",[34,87,88,89,92],{},"Half the people who land here are not subnetting at all — they have ",[38,90,91],{},"10.0.20.0/22"," in a ticket and need to know which addresses that actually covers, so they can write a firewall rule or hand a range to whoever is doing the scanning. The Calculate tab answers that directly: paste the block, read the IP range off the top row.",[34,94,95,96,100,101,104],{},"Two ranges get shown, and the difference matters more often than people expect. The ",[97,98,99],"strong",{},"IP range"," is the whole block, network and broadcast included — that is what an allow-list or a firewall object wants. The ",[97,102,103],{},"usable range"," is what you can put on an interface, which is two addresses narrower everywhere except /31 and /32. Writing a firewall rule against the usable range quietly excludes the broadcast address, and finding that out later is not fun.",[34,106,107,108,111],{},"It works the other way too, and this is the half most calculators skip. Type a range — ",[38,109,110],{},"10.0.0.5 - 10.0.0.20"," — and you get back the CIDR blocks that cover it exactly. Usually there is more than one, because an arbitrary range is almost never a subnet: those sixteen addresses take four blocks, and 172.16.5.3 to 172.16.9.200 takes thirteen. A firewall rule or an RIR form needs all of them, and getting that list by hand is where the afternoon goes.",[34,113,114],{},"Give it an address with a dotted mask instead and the CIDR notation comes back, which is the other direction people mean by a CIDR converter.",[46,116,118],{"id":117},"two-things-it-refuses-to-do","Two things it refuses to do",[34,120,121,124],{},[38,122,123],{},"010.0.0.1"," gets rejected rather than interpreted. That string is 8.0.0.1 to anything that reads the leading zero as octal and 10.0.0.1 to anything that does not, and quietly picking a side is how a firewall rule ends up on a network nobody intended. Strip the zero and try again.",[34,126,127],{},"A bare address becomes a /32, not a classful guess. Nothing has honoured class A/B/C since CIDR arrived in 1993, and answering \"/8\" for a 10.x host is a wrong answer wearing a helpful expression.",[46,129,131],{"id":130},"splitting","Splitting",[34,133,134],{},"Give it a block and a target prefix and you get the list — CIDR, network, usable range, broadcast — plus a CSV to paste into the plan you are actually maintaining. It caps at 512 rows, because a /8 divided into /30s is four million lines and nobody wants that in a browser tab. IPv6 works in the calculator, not the splitter; carving a /48 into /64s produces 65,536 rows that are more usefully described by a sentence than a table.",[34,136,137,138,143],{},"Want the whole prefix table to read rather than one answer at a time? That is the ",[139,140,142],"a",{"href":141},"/tools/subnet-cheat-sheet","subnet cheat sheet",", /32 down to /0 on one page.",[34,145,146,147,151,152,156],{},"Doing the reverse — labelling the physical boxes those addresses belong to — is a different job. The ",[139,148,150],{"href":149},"/tools/mac-address-lookup","MAC address lookup"," names the manufacturer behind an address you found on the wire, and the ",[139,153,155],{"href":154},"/tools/bulk-barcode-generator","bulk barcode generator"," prints the asset tags.",[158,159],"essential-faq-section",{":contactLink":160,":faqs":161,"title":162},"{\"text\":\"Documenting the equipment on those subnets?\",\"callActionText\":\"Talk to sales\",\"url\":\"/contacts\"}","[{\"title\":\"Masks and prefixes\",\"items\":[{\"question\":\"Why does /24 give 254 hosts and not 256?\",\"answer\":\"The first address in the block is the network address and the last is the broadcast address, so neither can be assigned to an interface. That leaves 254 on a /24. The exceptions are /31 and /32, which have no broadcast address at all.\"},{\"question\":\"What is the wildcard mask for?\",\"answer\":\"It is the subnet mask with every bit flipped, and Cisco ACLs and OSPF network statements want it instead of the mask. 255.255.255.0 becomes 0.0.0.255. It is shown next to the mask so you are not doing that subtraction in your head at 2am.\"},{\"question\":\"Can I enter 255.255.255.0 instead of /24?\",\"answer\":\"Yes, either after a slash or after a space, so you can paste a line straight out of ifconfig or a Windows ipconfig. A mask with gaps in it, like 255.0.255.0, gets rejected — that is not a valid mask, and no interface will accept it.\"}]},{\"title\":\"Ranges\",\"items\":[{\"question\":\"How do I calculate the IP address range from a CIDR block?\",\"answer\":\"The prefix tells you how many addresses the block holds, and they run consecutively from the network address. A /27 holds 32, so 192.168.2.0/27 covers 192.168.2.0 through 192.168.2.31. Paste the block into the Calculate tab and both the full range and the usable range come back without the arithmetic.\"},{\"question\":\"What IP range is 192.168.0.0/16?\",\"answer\":\"192.168.0.0 through 192.168.255.255 — 65,536 addresses, of which 65,534 can go on interfaces. It is the whole of the private 192.168 space defined by RFC 1918, which is why home routers hand out addresses inside it.\"},{\"question\":\"How do I convert an IP range back into CIDR?\",\"answer\":\"Type the range into the Calculate tab and read the blocks off the table. Expect more than one: a range only collapses into a single CIDR block when it starts on the right boundary and holds a power of two addresses. 192.168.1.5 to 192.168.1.10 needs four blocks, and there is no shorter honest answer.\"},{\"question\":\"What is the range of 192.168.2.0/27?\",\"answer\":\"192.168.2.0 through 192.168.2.31. The first is the network address and the last is the broadcast, so 192.168.2.1 to 192.168.2.30 are assignable — 30 hosts. The next block starts at 192.168.2.32.\"}]},{\"title\":\"Plans and overlaps\",\"items\":[{\"question\":\"Two blocks overlap. Is that always wrong?\",\"answer\":\"No. A summary route deliberately contains the specific routes underneath it, and that is a real overlap that is supposed to be there. The flag tells you the containment exists; deciding whether it was intentional is the part only you can do.\"},{\"question\":\"How many blocks can I paste at once?\",\"answer\":\"500. Past that the comparison is every block against every other one, and a browser tab is the wrong place for it. If your plan is bigger than 500 blocks you have an IPAM, and it should be doing this.\"},{\"question\":\"Does it check whether the addresses are actually in use?\",\"answer\":\"No, and nothing that runs in a browser can. This reads the arithmetic of what you typed. Finding out what answers on those addresses needs a scan from inside the network.\"}]}]","Subnetting — the questions that come up mid-task",[19,164],{":primaryButton":165,"subtitle":166,"title":167,":secondaryButton":168},"{\"text\":\"Start for Free\",\"url\":\"https://my.unio24.com/signup?utm_source=unio24-site&utm_medium=referral&utm_campaign=tools&utm_content=tools-subnet-calculator\"}","Start free with 50 assets: every laptop, switch and access point in one register with owner, location, warranty and a QR tag that opens the record from a phone.","Know the subnet. Know the box on it.","{\"text\":\"Book a Demo\",\"url\":\"/demo\"}",{"title":32,"searchDepth":170,"depth":170,"links":171},2,[],"Free CIDR and subnet calculator. Convert CIDR to an IP range or a range back to CIDR blocks, read the mask, wildcard and host counts, split a block, or check an IP plan for overlaps. Runs in your browser.","md",false,"cidr calculator, subnet calculator, cidr to ip range, ip range to cidr, cidr converter, cidr range calculator, ip range calculator, ip address range calculator, ip to cidr, ip subnet calculator, subnet mask calculator, cidr notation, vlsm calculator, wildcard mask calculator","en",{"schemaOrg":178},[179,190],{"@type":180,"name":181,"applicationCategory":182,"operatingSystem":183,"description":184,"url":185,"offers":186},"WebApplication","UNIO24 Subnet Calculator","BusinessApplication","Any","Free browser-based CIDR and subnet calculator that converts a CIDR block into its IP range and an arbitrary IP range back into the fewest CIDR blocks that cover it, derives network address, usable host range, broadcast, mask and wildcard for IPv4 and IPv6, splits a block into equal subnets, and checks a pasted IP plan for overlapping ranges.","https://unio24.com/tools/subnet-calculator",{"@type":187,"price":188,"priceCurrency":189},"Offer","0","USD",{"@type":191,"itemListElement":192},"BreadcrumbList",[193,198,201],{"@type":194,"position":195,"name":196,"item":197},"ListItem",1,"Home","https://unio24.com/",{"@type":194,"position":170,"name":199,"item":200},"Tools","https://unio24.com/tools",{"@type":194,"position":202,"name":203,"item":185},3,"Subnet Calculator",true,"/tools/subnet-calculator",{"title":6,"description":172},{"loc":205,"lastmod":208},"2026-09-03T02:44:27+03:00","tools/subnet-calculator",null,"TJvdZyNlb5l2tjYDctks5AHnm4vV4cgH0rUxSaW4Ss8",[],1788397932356]