{
  "title": "Tire size comparison calculator",
  "human_url": "https://happytails.ai/en/calculators/tire-size-comparison-calculator/",
  "agent_url": "https://happytails.ai/agents/en/calculators/tire-size-comparison-calculator/",
  "language": "en",
  "markdown_url": "https://happytails.ai/en/calculators/tire-size-comparison-calculator.md",
  "content": "Tire size comparison calculator\nCompare two tire sizes before you dig into fitment. See diameter, width, circumference and the nominal speedometer change side by side.\nHow can we improve this tool?\nReport a problem or share an idea.\nPlease leave out private information. Your message and the tool name go to our team via PostHog.\nHow to use Tire size comparison calculator\nEnter the reference and proposed metric tire sizes.\nChoose dimension and speed units, then enter an indicated speed.\nCompare the overlay and nominal changes, then download the table or report.\nUseful next steps\nFuel cost calculator\nSpeed\nMm to inches\nInches to cm\nCompare metric tire sizes\nEnter a reference size and a proposed size, such as 205/55R16 and 225/45R17. The first number is section width in millimeters. The middle number is sidewall height as a percentage of width. The number after R is wheel diameter in inches. P, LT and ZR markings are accepted, but load indexes, speed-rating suffixes and flotation sizes such as 31x10.5R15 are outside this input format.\nSee what changes, in millimeters or inches\nSidewall height equals width × aspect ratio ÷ 100. Overall diameter adds two sidewalls to the wheel diameter, using exactly 25.4 millimeters per inch. Circumference is π × diameter. The overlay uses one shared scale for both sizes. The detailed table includes absolute and percentage changes, plus nominal revolutions per kilometer and mile.\nRead the speedometer change in the right direction\nThe calculator assumes a speedometer calibrated exactly for the reference tire. With a larger proposed circumference, each revolution covers more distance, so nominal actual speed is higher than the displayed speed. With a smaller circumference, it is lower. For 205/55R16 to 225/45R17, an indicated 100 km/h corresponds to about 100.38 km/h under that assumption. Factory calibration error and loaded rolling radius are not included.\nTreat clearance as a geometric estimate\nHalf the diameter change gives the nominal ride-height change and the opposite change in radial wheel-arch space. Half the width change reduces inner and outer space if the wheel centerline stays unchanged. These figures do not model wheel offset, rim width, suspension travel, tire-model differences, wear, pressure or load. They do not establish fitment, safety, approval or legality for a vehicle.\nKeep the comparison\nDownload the comparison table as CSV, the overlay as SVG and the full calculation as a JSON report. The report includes unrounded values, assumptions and formula references. Everything is calculated in your browser; the tire sizes are not uploaded for processing.",
  "content_format": "text/plain",
  "visibility": "public",
  "links": [
    {
      "name": "Fuel cost calculator",
      "url": "https://happytails.ai/en/calculators/fuel-cost-calculator/"
    },
    {
      "name": "Speed",
      "url": "https://happytails.ai/en/unit-converters/speed/"
    },
    {
      "name": "Mm to inches",
      "url": "https://happytails.ai/en/unit-converters/mm-to-inches/"
    },
    {
      "name": "Inches to cm",
      "url": "https://happytails.ai/en/unit-converters/inches-to-cm/"
    }
  ],
  "tool": {
    "id": "tire-size-comparison-calculator",
    "category": "calculators",
    "built": true,
    "requirements": "Supports radial metric sizes with widths of 100–995 mm, aspect ratios of 10–100, and rim diameters of 8–60 inches in whole or half inches. These are calculation bounds, not a claim that every size exists. Results use nominal unloaded geometry and do not confirm vehicle compatibility.",
    "implementation": {
      "fields": [
        {
          "key": "referenceSize",
          "label": "Reference tire size",
          "value": "205/55R16",
          "type": "text",
          "help": "Metric radial size only, such as 205/55R16. This is the size the speedometer is assumed calibrated for."
        },
        {
          "key": "proposedSize",
          "label": "Proposed tire size",
          "value": "225/45R17",
          "type": "text",
          "help": "Optional P, LT and ZR markings are accepted. Leave out load indexes and speed-rating suffixes."
        },
        {
          "key": "dimensionUnit",
          "label": "Show dimensions in",
          "value": "mm",
          "type": "select",
          "values": [
            "mm",
            "in"
          ]
        },
        {
          "key": "indicatedSpeed",
          "label": "Indicated speed",
          "value": 100,
          "type": "number",
          "min": 0,
          "max": 1000,
          "step": "any",
          "help": "The speed shown on a speedometer calibrated exactly for the reference tire."
        },
        {
          "key": "speedUnit",
          "label": "Speed unit",
          "value": "km/h",
          "type": "select",
          "values": [
            "km/h",
            "mph"
          ]
        }
      ],
      "input": false,
      "live": true,
      "presentation": "metrics",
      "note": "Compare nominal unloaded dimensions, circumference and speedometer changes. Wheel offset, wheel width, tire-model differences, load, pressure and wear are not modeled. Clearance changes assume an unchanged wheel centerline and suspension. Results do not establish fitment, safety, approval or legality. Runs entirely in your browser.",
      "experience": {
        "automatic": true,
        "single": false,
        "inputMaxLength": 1000000,
        "inputMode": "text",
        "label": "Your text",
        "placeholder": "Type or paste your input…",
        "help": "Change the input or settings to update your result. Results update as you type. Up to 1,000,000 characters.",
        "action": null
      },
      "mode": "automatic",
      "interactive": false
    },
    "execution": "Browser interface",
    "api": null,
    "browser_agent": {
      "supported": true,
      "name": "run_current_tool",
      "discovery": "WebMCP on the human page in a supporting browser",
      "verification": "See audit/API-AUDIT.md; availability is not verification"
    }
  },
  "markdown": "# Tire size comparison calculator\n\n- Human page: https://happytails.ai/en/calculators/tire-size-comparison-calculator/\n- Markdown: https://happytails.ai/en/calculators/tire-size-comparison-calculator.md\n- Structured JSON: https://happytails.ai/agents/en/calculators/tire-size-comparison-calculator/index.json\n- Visibility: public\n\n## Tool capabilities\n\n| Property | Value |\n| --- | --- |\n| Tool ID | `tire-size-comparison-calculator` |\n| Category | calculators |\n| Implementation | Registered implementation. Registration alone is not a production-quality guarantee. |\n| Browser execution | Automatic updates after valid input or file selection. |\n| Browser processing | Browser; see tool notes for network behavior. |\n| HTTP API | Not callable through HTTP. |\n| Browser-agent interface | run_current_tool |\n\n### Implementation notes\n\nCompare nominal unloaded dimensions, circumference and speedometer changes. Wheel offset, wheel width, tire-model differences, load, pressure and wear are not modeled. Clearance changes assume an unchanged wheel centerline and suspension. Results do not establish fitment, safety, approval or legality. Runs entirely in your browser.\n\n### Inputs and settings\n\nNo free-text input is required. Use the file inputs and/or settings below.\n\n| Setting | Meaning | Control type | Default | Constraints |\n| --- | --- | --- | --- | --- |\n| `referenceSize` | Reference tire size | text | \"205/55R16\" |  |\n| `proposedSize` | Proposed tire size | text | \"225/45R17\" |  |\n| `dimensionUnit` | Show dimensions in | select | \"mm\" | Allowed: mm, in |\n| `indicatedSpeed` | Indicated speed | number | 100 | min=0 max=1000 step=any |\n| `speedUnit` | Speed unit | select | \"km/h\" | Allowed: km/h, mph |\n\n### Browser-agent workflow\n\n1. Open the human page in a browser that supports WebMCP.\n2. Discover the interface exposed by that page; use its actual schema.\n3. Select files on the page first when the tool requires files.\n4. Call `run_current_tool` with valid input and settings.\n5. Inspect the returned result or error and the displayed output. Retrieve files from the displayed download links.\n\nCalls do not automatically copy or download results. Browser permissions still apply. Interface availability alone is not proof of successful execution.\n\n### Planning specification\n\nSupports radial metric sizes with widths of 100–995 mm, aspect ratios of 10–100, and rim diameters of 8–60 inches in whole or half inches. These are calculation bounds, not a claim that every size exists. Results use nominal unloaded geometry and do not confirm vehicle compatibility.\n\nThis describes intended requirements. Use the implementation notes, interface schema and observed output to determine current support.\n\n### Complete machine-readable capability record\n\n```json\n{\n  \"id\": \"tire-size-comparison-calculator\",\n  \"category\": \"calculators\",\n  \"built\": true,\n  \"requirements\": \"Supports radial metric sizes with widths of 100–995 mm, aspect ratios of 10–100, and rim diameters of 8–60 inches in whole or half inches. These are calculation bounds, not a claim that every size exists. Results use nominal unloaded geometry and do not confirm vehicle compatibility.\",\n  \"implementation\": {\n    \"fields\": [\n      {\n        \"key\": \"referenceSize\",\n        \"label\": \"Reference tire size\",\n        \"value\": \"205/55R16\",\n        \"type\": \"text\",\n        \"help\": \"Metric radial size only, such as 205/55R16. This is the size the speedometer is assumed calibrated for.\"\n      },\n      {\n        \"key\": \"proposedSize\",\n        \"label\": \"Proposed tire size\",\n        \"value\": \"225/45R17\",\n        \"type\": \"text\",\n        \"help\": \"Optional P, LT and ZR markings are accepted. Leave out load indexes and speed-rating suffixes.\"\n      },\n      {\n        \"key\": \"dimensionUnit\",\n        \"label\": \"Show dimensions in\",\n        \"value\": \"mm\",\n        \"type\": \"select\",\n        \"values\": [\n          \"mm\",\n          \"in\"\n        ]\n      },\n      {\n        \"key\": \"indicatedSpeed\",\n        \"label\": \"Indicated speed\",\n        \"value\": 100,\n        \"type\": \"number\",\n        \"min\": 0,\n        \"max\": 1000,\n        \"step\": \"any\",\n        \"help\": \"The speed shown on a speedometer calibrated exactly for the reference tire.\"\n      },\n      {\n        \"key\": \"speedUnit\",\n        \"label\": \"Speed unit\",\n        \"value\": \"km/h\",\n        \"type\": \"select\",\n        \"values\": [\n          \"km/h\",\n          \"mph\"\n        ]\n      }\n    ],\n    \"input\": false,\n    \"live\": true,\n    \"presentation\": \"metrics\",\n    \"note\": \"Compare nominal unloaded dimensions, circumference and speedometer changes. Wheel offset, wheel width, tire-model differences, load, pressure and wear are not modeled. Clearance changes assume an unchanged wheel centerline and suspension. Results do not establish fitment, safety, approval or legality. Runs entirely in your browser.\",\n    \"experience\": {\n      \"automatic\": true,\n      \"single\": false,\n      \"inputMaxLength\": 1000000,\n      \"inputMode\": \"text\",\n      \"label\": \"Your text\",\n      \"placeholder\": \"Type or paste your input…\",\n      \"help\": \"Change the input or settings to update your result. Results update as you type. Up to 1,000,000 characters.\",\n      \"action\": null\n    },\n    \"mode\": \"automatic\",\n    \"interactive\": false\n  },\n  \"execution\": \"Browser interface\",\n  \"api\": null,\n  \"browser_agent\": {\n    \"supported\": true,\n    \"name\": \"run_current_tool\",\n    \"discovery\": \"WebMCP on the human page in a supporting browser\",\n    \"verification\": \"See audit/API-AUDIT.md; availability is not verification\"\n  }\n}\n```\n\n## Page guide\n\nCompare two tire sizes before you dig into fitment. See diameter, width, circumference and the nominal speedometer change side by side.\n\nHow can we improve this tool?\n\nReport a problem or share an idea.\n\nPlease leave out private information. Your message and the tool name go to our team via PostHog.\n\n### How to use Tire size comparison calculator\n\n1. Enter the reference and proposed metric tire sizes.\n2. Choose dimension and speed units, then enter an indicated speed.\n3. Compare the overlay and nominal changes, then download the table or report.\n\n## Useful next steps\n\n- [Fuel cost calculator](https://happytails.ai/en/calculators/fuel-cost-calculator/) ([Markdown](https://happytails.ai/en/calculators/fuel-cost-calculator.md))\n\n- [Speed](https://happytails.ai/en/unit-converters/speed/) ([Markdown](https://happytails.ai/en/unit-converters/speed.md))\n\n- [Mm to inches](https://happytails.ai/en/unit-converters/mm-to-inches/) ([Markdown](https://happytails.ai/en/unit-converters/mm-to-inches.md))\n\n- [Inches to cm](https://happytails.ai/en/unit-converters/inches-to-cm/) ([Markdown](https://happytails.ai/en/unit-converters/inches-to-cm.md))\n\n## Compare metric tire sizes\n\nEnter a reference size and a proposed size, such as 205/55R16 and 225/45R17. The first number is section width in millimeters. The middle number is sidewall height as a percentage of width. The number after R is wheel diameter in inches. P, LT and ZR markings are accepted, but load indexes, speed-rating suffixes and flotation sizes such as 31x10.5R15 are outside this input format.\n\n### See what changes, in millimeters or inches\n\nSidewall height equals width × aspect ratio ÷ 100. Overall diameter adds two sidewalls to the wheel diameter, using exactly 25.4 millimeters per inch. Circumference is π × diameter. The overlay uses one shared scale for both sizes. The detailed table includes absolute and percentage changes, plus nominal revolutions per kilometer and mile.\n\n### Read the speedometer change in the right direction\n\nThe calculator assumes a speedometer calibrated exactly for the reference tire. With a larger proposed circumference, each revolution covers more distance, so nominal actual speed is higher than the displayed speed. With a smaller circumference, it is lower. For 205/55R16 to 225/45R17, an indicated 100 km/h corresponds to about 100.38 km/h under that assumption. Factory calibration error and loaded rolling radius are not included.\n\n### Treat clearance as a geometric estimate\n\nHalf the diameter change gives the nominal ride-height change and the opposite change in radial wheel-arch space. Half the width change reduces inner and outer space if the wheel centerline stays unchanged. These figures do not model wheel offset, rim width, suspension travel, tire-model differences, wear, pressure or load. They do not establish fitment, safety, approval or legality for a vehicle.\n\n### Keep the comparison\n\nDownload the comparison table as CSV, the overlay as SVG and the full calculation as a JSON report. The report includes unrounded values, assumptions and formula references. Everything is calculated in your browser; the tire sizes are not uploaded for processing.\n"
}