HVAC duct sizing calculator
HVAC duct sizing calculator: any two of duct size (round or rectangular), airflow, velocity and friction rate. Round and rectangular equivalents, nearest standard sizes, friction loss per 100 ft (Darcy-Weisbach, Colebrook), velocity pressure, design checks. Equal-friction sizing, fixed-depth ducts, IP or SI. Shows every step with the numbers. $0.002 USDC per call.
Answeringour last check, 2026-10-10
1 of 1checks answered this week
169 msmedian answer time
$0.002listed price per call
$0.002price it asked us
Paid test badge: not yet. The checks above are free: we call the tool without paying and read the payment request it sends back. The Verified badge needs paid calls whose answers match the promised output, and nobody can buy a badge.
Endpoint
POST https://x402-agent-api.onrender.com/api/v1/hvac-duct-size
| Category | Everything else |
|---|---|
| Provider host | x402-agent-api.onrender.com |
| Networks | eip155:8453 |
| Payment schemes | exact |
| Self-reported calls, 30 days | 2 from 2 payers (the provider's figure, not ours) |
Our checks, last 30 days
| Day | Result | HTTP | Asked | Time |
|---|---|---|---|---|
| 2026-10-10 | valid payment request | 402 | $0.002 | 169 ms |
Example input (from the provider)
{
"body": {
"airflow": 1000,
"friction_rate": 0.08
},
"bodyType": "json",
"method": "POST",
"type": "http"
}
Promised output schema (from the provider)
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"properties": {
"input": {
"additionalProperties": false,
"properties": {
"body": {
"additionalProperties": false,
"properties": {
"airflow": {
"description": "Airflow: CFM (IP) or L/s (SI).",
"exclusiveMinimum": 0,
"type": "number"
},
"diameter": {
"description": "Round duct diameter: in (IP) or mm (SI).",
"exclusiveMinimum": 0,
"type": "number"
},
"friction_rate": {
"description": "Friction loss: in. w.g. per 100 ft (IP, typically 0.05-0.15) or Pa/m (SI, typically 0.4-1.2). With airflow, this is equal-friction sizing.",
"exclusiveMinimum": 0,
"type": "number"
},
"height": {
"description": "Rectangular height: in or mm.",
"exclusiveMinimum": 0,
"type": "number"
},
"units": {
"default": "IP",
"description": "\"IP\" (\u00b0F, CFM, in, BTU) or \"SI\" (\u00b0C, L/s, mm, kW). Default IP. Applies to inputs and results.",
"enum": [
"IP",
"SI"
],
"type": "string"
},
"velocity": {
"description": "Air velocity: FPM (IP) or m/s (SI).",
"exclusiveMinimum": 0,
"type": "number"
},
"width": {
"description": "Rectangular width: in or mm. With height, the duct size; alone, a fixed side (e.g. a ceiling depth) the other side is solved for.",
"exclusiveMinimum": 0,
"type": "number"
}
},
"type": "object"
},
"bodyType": {
"enum": [
"json",
"form-data",
"text"
],
"type": "string"
},
"method": {
"enum": [
"POST"
],
"type": "string"
},
"type": {
"const": "http",
"type": "string"
}
},
"required": [
"type",
"method",
"bodyType",
"body"
],
"type": "object"
},
"output": {
"properties": {
"example": {
"type": "object"
},
"type": {
"type": "string"
}
},
"required": [
"type"
],
"type": "object"
}
},
"required": [
"input"
],
"type": "object"
}