Rainfall rate converter
Convert rain intensity between five units: 25.4 mm/h is exactly 1 in/h and 1 mm/min is 60 mm/h, so weather bulletins, gauge logs and stormwater sheets from different countries agree. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Numeric rainfall intensity
- 25.4
- Source unit
- mm/h
- Target unit
- in/h
- Result
- 1
- From label
- millimeters per hour
- To label
- inches per hour
- Mm per h
- 25.4
A rainfall rate converter turns precipitation intensity written in one unit into another without hunting meteorology handbooks, drainage design tables, or mixed SI and US customary factors.
Supported units and how the conversion is computed
The converter accepts five rainfall-intensity families under stable canonical codes: mm/h for millimeters per hour, in/h for inches per hour, L/m2/h for liters per square meter per hour, cm/h for centimeters per hour, and mm/min for millimeters per minute.
Factors follow SI depth definitions and the international inch: one liter spread over one square meter is exactly one millimeter of water depth, so L/m2/h equals mm/h numerically; one centimeter per hour is ten millimeters per hour; one millimeter per minute is sixty millimeters per hour; and one inch per hour is exactly twenty-five point four millimeters per hour.
Because the intermediate is always millimeters per hour, converting A to B and B to A is consistent up to the published rounding of twelve decimal places, and there is no pairwise matrix that can drift out of sync. Volumetric river discharge, pump flow in liters per second, and snow water equivalent without a stated time base are intentionally out of scope so hydrology, civil drainage, and weather users who expect precipitation depth rates get predictable results.
Where rainfall rates get converted
Use the free in-browser rainfall rate converter when you need a quick millimeters-per-hour-to-inches-per-hour, liters-per-square-meter-per-hour-to-mm/h, or centimeters-per-hour-to-mm/min check while reading a weather bulletin, stormwater design brief, rain-gauge log, irrigation schedule, or homework problem. Open the page, enter the number and units, and copy the result without installing a spreadsheet, a unit library, or a desktop calculator pack. Source inputs follow the same retention rules as other KIT parse items, and results are safe to cache because the algorithm is fully deterministic.
Authors shipping mobile apps or chatbots can map the result and formula fields directly into cards that show both the number and the conversion path operators, students, and field technicians expect on paper.
What you can do with it
Stormwater and drainage design
Convert design-storm intensities between mm/h and in/h so European and North American codes, IDF curves, and pipe-sizing sheets share one rate language.
Weather bulletins and rain gauges
Translate station reports in L/m²/h or mm/min into millimeters or inches per hour for public alerts, apps, and post-event analysis.
FAQ
Is L/m²/h the same as mm/h?
The converter still accepts both codes for clarity in different domains.
What happens if I send an unknown unit?
The error message names the field and lists supported units (mm/h, in/h, L/m2/h, cm/h, mm/min). Validation failures are not charged.
Is the rainfall rate converter free?
The browser tool runs free on your device.
Which inch definition is used?
The international inch of exactly 25.4 millimeters. One inch per hour therefore converts to exactly 25.4 millimeters per hour.
How do I convert millimeters per minute to millimeters per hour?
Multiply by 60. One millimeter per minute is sixty millimeters per hour, which helps when a gauge logs short bursts and a bulletin or design sheet expects hourly rates.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/conv/rainfall-rate \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"value":25.4,"from":"mm/h","to":"in/h"}'const res = await fetch("https://api.kit.forhosting.com/conv/rainfall-rate", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"value": 25.4,
"from": "mm/h",
"to": "in/h"
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/conv/rainfall-rate",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"value": 25.4,
"from": "mm/h",
"to": "in/h"
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/conv/rainfall-rate", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"value":25.4,"from":"mm/h","to":"in/h"}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"value":25.4,"from":"mm/h","to":"in/h"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/conv/rainfall-rate", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"value": 25.4,
"from": "mm/h",
"to": "in/h"
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "conv.rainfall_rate",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
The browser tool runs free on your device; the prepaid API charges $0.002 per successful item when pipelines need the same contract from servers and automation.
Supported units and how the conversion is computed
Friendly aliases such as millimeters per hour, inches per hour, liters per square meter per hour, L/m²/h, centimetres per hour, and millimeters per minute are normalized case-insensitively so forms and APIs can pass either short codes or full names. Every request multiplies the input value by the exact millimeters-per-hour factor for the source, then divides by the millimeters-per-hour factor for the target.
Request shape, response fields, and unknown-unit errors
The error message names the bad field and lists the supported set so clients can correct forms without guessing. Negative values are allowed when you need signed intensity deltas in research pipelines; zero converts cleanly to zero in every target unit. Send a JSON body with three required fields: value as a finite number, from as the source unit string, and to as the target unit string. Aliases amount, quantity, rate, and intensity are accepted for value; unit_from and source for from; unit_to and target for to. On success the response echoes the canonical from and to codes, human-readable from_label and to_label strings, the converted result, the intermediate mm_per_h quantity in millimeters per hour, the dimensionless factor from source to target, a short formula line suitable for UI display, the method tag rainfall_rate_mmh_base, and the fixed list of units_supported. Missing value, non-finite numbers such as NaN or Infinity, missing unit fields, and any token that does not map to a supported unit fail with invalid_input and are not charged after the engine rejects the request. Identical inputs always yield identical JSON because the path is pure arithmetic with no randomness, no remote lookup, and no dependence on the wall clock, which makes the endpoint safe to pin in continuous-integration goldens and SDK contract tests. Storm-peak rates and light drizzle share the same code path, so extreme magnitude pairs remain well-defined as long as IEEE double precision can represent the intermediate millimeters-per-hour product.
Browser use, API pricing, and everyday workflows
Switch to the prepaid API when a hydrology dashboard, municipal drainage model, agricultural advisory tool, climate-data pipeline, or classroom homework checker must convert precipitation intensity at scale under a stable KIT contract at $0.002 per successful item; validation failures that raise invalid_input do not consume balance after rejection. Pair this endpoint with the volumetric flow converter when a product pipeline needs both catchment runoff volume rates and rainfall depth rates, or call it alone when search traffic is specifically for rainfall rate conversion—millimeters per hour, inches per hour, and liters per square meter per hour—rather than a general unit switchboard.
Integration use cases
Irrigation and climate pipelines
Normalize forecast precipitation intensity tags to mm/h or in/h in automation scripts with a prepaid, deterministic API contract.
Technical questions
How do I convert mm/h to inches per hour?
Send JSON with value set to the intensity, from: "mm/h", and to: "in/h". The response includes result in inches per hour and an intermediate mm_per_h field.