GrowVPD Pro API Documentation

Quick Start

The GrowVPD Pro API is completely free and requires no authentication. All endpoints return JSON. Just send a GET request and you are ready to go.

ⓘ

The API is currently served at https://api.growvpd.pro. This will transition to https://api.growvpd.pro in the near future. All endpoint paths will remain identical.

Terminal

# Calculate VPD for 25C and 60% humidity
curl "https://api.growvpd.pro/v1/vpd?temp=25&humidity=60"

# Get environment targets for mid-flower stage
curl "https://api.growvpd.pro/v1/stage?stage=mid_flower&medium=coco"

JavaScript

const BASE = "https://api.growvpd.pro";

async function getVPD(temp, humidity) {
  const res = await fetch(
    `${BASE}/v1/vpd?temp=${temp}&humidity=${humidity}`
  );
  return res.json();
}

// Usage
const data = await getVPD(25, 60);
console.log(data.vpd);     // 1.27
console.log(data.status);  // "slightly_high"

Python

import requests

BASE = "https://api.growvpd.pro"

def get_vpd(temp, humidity):
    r = requests.get(f"{BASE}/v1/vpd", params={
        "temp": temp,
        "humidity": humidity
    })
    return r.json()

data = get_vpd(25, 60)
print(data["vpd"])     # 1.27
print(data["status"])  # "slightly_high"

⚡

Rate limits: Currently none. Be reasonable with requests. If you plan to make high-volume calls, please reach out at support@growvpd.pro.

🌱 Core VPD

GET /v1/vpd

Calculate VPD (Vapor Pressure Deficit) from temperature and humidity. Returns VPD value, leaf VPD, status classification, and optimal ranges for all growth stages.

Parameter	Type	Default	Description
temprequired	number	-	Air temperature
humidityrequired	number	-	Relative humidity (%)
leaf_offset	number	2.0	Leaf temperature offset below air temp
unit	string	c	Temperature unit: `c` (Celsius) or `f` (Fahrenheit)

Try it

GET /v1/vpd?temp=25&humidity=60

{
  "vpd": 1.27,
  "vpd_leaf": 1.09,
  "status": "slightly_high",
  "temperature": 25,
  "humidity": 60,
  "leaf_temperature": 23,
  "dewpoint": 16.7,
  "unit": "celsius",
  "stages": {
    "clone_seedling": { "min": 0.4, "max": 0.8, "status": "too_high" },
    "early_veg": { "min": 0.6, "max": 1.0, "status": "too_high" },
    "late_veg": { "min": 0.8, "max": 1.2, "status": "slightly_high" },
    "early_flower": { "min": 1.0, "max": 1.4, "status": "optimal" },
    "mid_flower": { "min": 1.2, "max": 1.5, "status": "optimal" },
    "late_flower": { "min": 1.2, "max": 1.6, "status": "optimal" }
  }
}

GET /v1/target

Reverse VPD calculator. Given a target VPD (or growth stage) and either temperature or humidity, calculates the missing variable. Useful for finding what humidity to aim for at a given temperature.

Parameter	Type	Default	Description
vpd	number	-	Target VPD value (kPa). Provide this or `stage`.
stage	string	-	Growth stage (uses midpoint VPD). One of: clone_seedling, early_veg, late_veg, early_flower, mid_flower, late_flower
temp	number	-	Known temperature (solves for humidity)
humidity	number	-	Known humidity (solves for temperature)
leaf_offset	number	2.0	Leaf temperature offset
unit	string	c	Temperature unit: `c` or `f`

Try it

GET /v1/target?vpd=1.2&temp=25

{
  "target_vpd": 1.2,
  "known_variable": "temperature",
  "known_value": 25,
  "solved_variable": "humidity",
  "solved_value": 62.1,
  "leaf_offset": 2.0,
  "unit": "celsius",
  "verification": {
    "actual_vpd": 1.2,
    "vpd_leaf": 1.03
  }
}

GET /v1/chart

Generate a VPD heatmap data matrix. Returns a 2D grid of VPD values across a temperature and humidity range, with zone classifications. Perfect for building visual VPD charts.

Parameter	Type	Default	Description
temp_min	number	15	Minimum temperature
temp_max	number	35	Maximum temperature
temp_step	number	1	Temperature step size
rh_min	number	30	Minimum relative humidity (%)
rh_max	number	90	Maximum relative humidity (%)
rh_step	number	5	Humidity step size
leaf_offset	number	2	Leaf temperature offset
stage	string	-	Growth stage for zone classification

Try it

GET /v1/chart?temp_min=18&temp_max=30&stage=mid_flower

{
  "temp_range": [18, 19, 20, ..., 30],
  "rh_range": [30, 35, 40, ..., 90],
  "stage": "mid_flower",
  "stage_range": { "min": 1.2, "max": 1.5 },
  "leaf_offset": 2,
  "matrix": [
    {
      "temp": 18,
      "values": [
        { "rh": 30, "vpd": 1.44, "zone": "optimal" },
        { "rh": 35, "vpd": 1.34, "zone": "optimal" },
        // ... more humidity values
      ]
    },
    // ... more temperature rows
  ]
}

GET /v1/batch

Batch VPD calculations with aggregated statistics. Submit multiple temperature/humidity readings and receive individual VPD values plus min, max, average, and standard deviation across the set.

Parameter	Type	Default	Description
readingsrequired	JSON array	-	Array of `{"temp":N, "humidity":N}` objects (URL-encoded)
leaf_offset	number	2.0	Leaf temperature offset

Try it

GET /v1/batch?readings=[{"temp":25,"humidity":60},{"temp":26,"humidity":55}]

{
  "readings": [
    {
      "temperature": 25,
      "humidity": 60,
      "vpd": 1.27,
      "vpd_leaf": 1.09,
      "status": "slightly_high"
    },
    {
      "temperature": 26,
      "humidity": 55,
      "vpd": 1.51,
      "vpd_leaf": 1.31,
      "status": "high"
    }
  ],
  "statistics": {
    "count": 2,
    "vpd_min": 1.27,
    "vpd_max": 1.51,
    "vpd_avg": 1.39,
    "vpd_std_dev": 0.12
  }
}

☀ Light & DLI

GET /v1/dli

Daily Light Integral calculator. Compute DLI from PPFD and photoperiod (forward), or find the required PPFD to hit a target DLI (reverse). Includes optimal DLI ranges per growth stage.

Parameter	Type	Default	Description
ppfd	number	-	Photosynthetic Photon Flux Density (umol/m2/s)
hours	number	-	Photoperiod in hours
dli	number	-	Target DLI (mol/m2/day) for reverse calculation

Try it

GET /v1/dli?ppfd=600&hours=12

{
  "ppfd": 600,
  "hours": 12,
  "dli": 25.92,
  "mode": "forward",
  "stage_targets": {
    "clone_seedling": { "dli_min": 6, "dli_max": 12 },
    "early_veg": { "dli_min": 15, "dli_max": 25 },
    "late_veg": { "dli_min": 25, "dli_max": 35 },
    "early_flower": { "dli_min": 30, "dli_max": 40 },
    "mid_flower": { "dli_min": 35, "dli_max": 50 },
    "late_flower": { "dli_min": 30, "dli_max": 45 }
  }
}

GET /v1/light

Comprehensive light calculator. Estimates PPFD from wattage and area, calculates DLI, evaluates light intensity for a given growth stage, and provides efficiency metrics.

Parameter	Type	Default	Description
ppfd	number	-	Known PPFD (if available)
hours	number	-	Photoperiod in hours
watts	number	-	Light wattage (for PPFD estimation)
efficiency	number	2.5	LED efficiency (umol/J)
area	number	-	Grow area in m2
height	number	-	Light height in meters
stage	string	-	Growth stage for evaluation

Try it

GET /v1/light?watts=600&area=1.44&hours=12&stage=mid_flower

{
  "ppfd_estimated": 1041.7,
  "dli": 45.0,
  "watts": 600,
  "area_m2": 1.44,
  "watts_per_m2": 416.7,
  "efficiency_umol_j": 2.5,
  "hours": 12,
  "stage": "mid_flower",
  "stage_evaluation": {
    "ppfd_status": "optimal",
    "ppfd_target": { "min": 600, "max": 1200 },
    "dli_status": "optimal",
    "dli_target": { "min": 35, "max": 50 }
  },
  "daily_energy_kwh": 7.2
}

🌿 Growing Stages

GET /v1/stage

Get comprehensive environment targets for a growth stage. Returns optimal ranges for VPD, temperature, humidity, PPFD, DLI, CO2, EC, pH, and watering frequency. Optionally tailored to a growing medium.

Parameter	Type	Default	Description
stage	string	-	Stage name or `"all"` for every stage. Options: clone_seedling, early_veg, late_veg, early_flower, mid_flower, late_flower
medium	string	-	Growing medium: `soil`, `coco`, `hydro`, `dwc`

Try it

GET /v1/stage?stage=mid_flower&medium=coco

{
  "stage": "mid_flower",
  "medium": "coco",
  "targets": {
    "vpd": { "min": 1.2, "max": 1.5, "ideal": 1.35 },
    "temperature": { "day_min": 24, "day_max": 28, "night_min": 18, "night_max": 22 },
    "humidity": { "min": 40, "max": 50 },
    "ppfd": { "min": 600, "max": 1200 },
    "dli": { "min": 35, "max": 50 },
    "co2": { "min": 800, "max": 1200 },
    "ec": { "min": 1.6, "max": 2.2 },
    "ph": { "min": 5.8, "max": 6.2 }
  },
  "watering": {
    "frequency": "2-4 times daily",
    "runoff_target": "10-20%"
  },
  "notes": [
    "Peak nutrient uptake period",
    "Coco requires more frequent fertigation than soil",
    "Monitor trichome development closely"
  ]
}

GET /v1/schedule

Generate a full grow timeline with week-by-week stage progression. Returns duration and environment targets for each stage, customized by plant type and growing medium.

Parameter	Type	Default	Description
type	string	-	Plant type: `photo` (photoperiod) or `auto` (autoflower)
medium	string	-	Growing medium: `soil`, `coco`, `hydro`, `dwc`

Try it

GET /v1/schedule?type=auto&medium=coco

{
  "type": "auto",
  "medium": "coco",
  "total_weeks": 10,
  "light_schedule": "20/4 or 18/6 throughout",
  "stages": [
    {
      "stage": "clone_seedling",
      "weeks": "1-1",
      "duration_weeks": 1,
      "vpd": { "min": 0.4, "max": 0.8 },
      "temp": { "min": 22, "max": 26 },
      "humidity": { "min": 65, "max": 80 }
    },
    {
      "stage": "early_veg",
      "weeks": "2-3",
      "duration_weeks": 2,
      "vpd": { "min": 0.6, "max": 1.0 },
      "temp": { "min": 22, "max": 28 },
      "humidity": { "min": 55, "max": 70 }
    },
    // ... remaining stages
  ]
}

🔍 Diagnostics

GET /v1/diagnose

Full environment diagnosis with a 0-100 health score. Analyzes temperature, humidity, VPD, pH, EC, PPFD, CO2, and night temperature. Returns issues found, severity levels, and actionable recommendations.

Parameter	Type	Default	Description
temprequired	number	-	Air temperature
humidityrequired	number	-	Relative humidity (%)
stage	string	-	Growth stage for context-aware diagnosis
medium	string	-	Growing medium
ppfd	number	-	Current PPFD
ph	number	-	Nutrient solution pH
ec	number	-	Nutrient solution EC (mS/cm)
co2	number	-	CO2 level (ppm)
night_temp	number	-	Night temperature
unit	string	c	Temperature unit: `c` or `f`

Try it

GET /v1/diagnose?temp=32&humidity=75&stage=late_flower&ph=7.5

{
  "health_score": 35,
  "overall_status": "critical",
  "vpd": 1.19,
  "temperature": 32,
  "humidity": 75,
  "stage": "late_flower",
  "issues": [
    {
      "parameter": "temperature",
      "severity": "high",
      "message": "Temperature too high for late flower (32C, target 20-26C)",
      "recommendation": "Increase ventilation, consider AC. High temps degrade terpenes and potency."
    },
    {
      "parameter": "humidity",
      "severity": "critical",
      "message": "Humidity critically high for late flower (75%, target 35-45%)",
      "recommendation": "Immediate action: run dehumidifier, increase airflow. Botrytis (bud rot) risk is extreme."
    },
    {
      "parameter": "ph",
      "severity": "medium",
      "message": "pH too high (7.5, target 6.0-6.5)",
      "recommendation": "Lower pH with pH Down. Nutrient lockout likely at this pH."
    }
  ],
  "mold_risk": "extreme",
  "dewpoint": 27.3
}

GET /v1/deficit

Symptom-based nutrient deficiency diagnosis. Describe visible plant symptoms and get ranked possible deficiencies with confidence scores, affected nutrients, and treatment recommendations.

Parameter	Type	Default	Description
symptomsrequired	string	-	Comma-separated symptom keywords. Examples: `yellow_lower_leaves`, `brown_spots`, `curling_up`, `purple_stems`, `slow_growth`, `burnt_tips`
ph	number	-	Current pH (helps narrow diagnosis)
medium	string	-	Growing medium

Try it

GET /v1/deficit?symptoms=yellow_lower_leaves,brown_spots&ph=7.2

{
  "symptoms": ["yellow_lower_leaves", "brown_spots"],
  "ph": 7.2,
  "ph_warning": "pH is above optimal range. Nutrient lockout likely contributing to symptoms.",
  "possible_deficiencies": [
    {
      "nutrient": "Calcium",
      "symbol": "Ca",
      "confidence": 0.85,
      "mobility": "immobile",
      "symptoms_matched": ["brown_spots"],
      "treatment": "Add Cal-Mag supplement. Lower pH to 6.0-6.5 for better uptake."
    },
    {
      "nutrient": "Nitrogen",
      "symbol": "N",
      "confidence": 0.78,
      "mobility": "mobile",
      "symptoms_matched": ["yellow_lower_leaves"],
      "treatment": "Increase nitrogen in feed. Mobile nutrient: lower leaves affected first."
    },
    {
      "nutrient": "Potassium",
      "symbol": "K",
      "confidence": 0.52,
      "mobility": "mobile",
      "symptoms_matched": ["brown_spots", "yellow_lower_leaves"],
      "treatment": "Increase K in bloom nutrients. Check for salt buildup in medium."
    }
  ],
  "general_advice": "Priority: lower pH to 6.0-6.5 first, then reassess after 3-5 days."
}

GET /v1/dewpoint

Calculate dewpoint temperature, mold/condensation risk assessment, and safe night temperature minimum. Essential for preventing bud rot and mildew.

Parameter	Type	Default	Description
temprequired	number	-	Air temperature
humidityrequired	number	-	Relative humidity (%)
unit	string	c	Temperature unit: `c` or `f`

Try it

GET /v1/dewpoint?temp=25&humidity=70

{
  "temperature": 25,
  "humidity": 70,
  "dewpoint": 19.2,
  "unit": "celsius",
  "mold_risk": "moderate",
  "condensation_risk": "low",
  "safe_night_temp_min": 21.2,
  "margin_to_dewpoint": 5.8,
  "recommendations": [
    "Night temperature must stay above 21.2C to prevent condensation",
    "Consider dehumidification if humidity rises above 75%"
  ]
}

🥳 Nutrients & Feeding

GET /v1/nutrient

Get EC, pH, and PPM targets for a given growth stage and medium. Includes medium-specific tips, flush schedules, and adjustments based on your water source EC.

Parameter	Type	Default	Description
stagerequired	string	-	Growth stage
medium	string	-	Growing medium: `soil`, `coco`, `hydro`, `dwc`
water_ec	number	-	Base water EC (mS/cm) for adjusted targets

Try it

GET /v1/nutrient?stage=mid_flower&medium=coco&water_ec=0.3

{
  "stage": "mid_flower",
  "medium": "coco",
  "water_ec": 0.3,
  "targets": {
    "ec": { "min": 1.6, "max": 2.2, "adjusted_min": 1.3, "adjusted_max": 1.9 },
    "ph": { "min": 5.8, "max": 6.2 },
    "ppm_500": { "min": 800, "max": 1100 },
    "ppm_700": { "min": 1120, "max": 1540 }
  },
  "npk_ratio": "1-3-2 (bloom focus)",
  "tips": [
    "Coco is inert - all nutrients must come from solution",
    "Always include Cal-Mag with coco (0.3-0.5 EC)",
    "Feed every watering, no plain water days",
    "Target 10-20% runoff to prevent salt buildup"
  ],
  "flush_schedule": "Flush with pH'd water at EC 0.3 every 2 weeks"
}

GET /v1/co2

CO2 enrichment calculator. Determine how much CO2 gas is needed to reach a target concentration in your grow room, and get stage-appropriate CO2 recommendations.

Parameter	Type	Default	Description
room_m3	number	-	Room volume in cubic meters
target_ppm	number	1200	Target CO2 concentration (ppm)
current_ppm	number	400	Current ambient CO2 (ppm)
stage	string	-	Growth stage for recommendations

Try it

GET /v1/co2?room_m3=2.5&target_ppm=1200&stage=mid_flower

{
  "room_m3": 2.5,
  "current_ppm": 400,
  "target_ppm": 1200,
  "co2_needed_liters": 2.0,
  "co2_needed_grams": 3.93,
  "stage": "mid_flower",
  "stage_recommendation": {
    "optimal_ppm": { "min": 800, "max": 1200 },
    "benefit": "10-30% yield increase with adequate light (>600 PPFD)"
  },
  "safety": {
    "human_safe": true,
    "osha_limit": 5000,
    "note": "Target level is safe for humans. Ensure ventilation during lights-off."
  },
  "tips": [
    "CO2 only benefits plants during lights-on period",
    "Seal room and disable exhaust during CO2 injection",
    "Higher CO2 allows higher temperatures (up to 30C)"
  ]
}

GET /v1/irrigation

Watering volume and frequency calculator. Computes optimal water volume per pot based on pot size, medium, growth stage, and current environment conditions. Supports multiple plants.

Parameter	Type	Default	Description
pot_sizerequired	number	-	Pot volume in liters
medium	string	-	Growing medium: `soil`, `coco`, `hydro`, `dwc`
stage	string	-	Growth stage
vpd	number	-	Current VPD (affects transpiration rate)
temp	number	-	Current temperature
plants	number	-	Number of plants (multiplies total)

Try it

GET /v1/irrigation?pot_size=11&medium=coco&stage=mid_flower&vpd=1.3&plants=4

{
  "pot_size_liters": 11,
  "medium": "coco",
  "stage": "mid_flower",
  "plants": 4,
  "per_plant": {
    "water_ml": 2750,
    "frequency": "2-4 times daily",
    "runoff_target_pct": 15
  },
  "total": {
    "water_ml": 11000,
    "water_liters": 11.0,
    "daily_total_liters": 33.0
  },
  "adjustments": {
    "vpd_factor": "VPD 1.3 is optimal, no adjustment needed",
    "temp_factor": null
  },
  "tips": [
    "Water until 10-20% runoff each time",
    "Never let coco dry out completely",
    "Check runoff EC to monitor salt buildup"
  ]
}

🔨 Equipment & Environment

GET /v1/room

Room equipment sizing calculator. Given your tent/room dimensions and light wattage, get recommended ventilation (CFM), humidifier/dehumidifier capacity, and fan sizing. Accounts for heat load from lights.

Parameter	Type	Default	Description
lengthrequired	number	-	Room length in meters
widthrequired	number	-	Room width in meters
height	number	2	Room height in meters
lights_watts	number	-	Total light wattage
target_temp	number	25	Target temperature
ambient_temp	number	22	Ambient/intake temperature
plants	number	4	Number of plants
target_humidity	number	55	Target humidity (%)

Try it

GET /v1/room?length=1.2&width=1.2&lights_watts=600&plants=4

{
  "room": {
    "length_m": 1.2,
    "width_m": 1.2,
    "height_m": 2,
    "area_m2": 1.44,
    "volume_m3": 2.88
  },
  "ventilation": {
    "cfm_min": 102,
    "cfm_recommended": 152,
    "exchanges_per_hour": 3,
    "fan_size_inches": 4
  },
  "climate": {
    "heat_output_btu": 2047,
    "cooling_needed": true,
    "dehumidifier_pints_per_day": 8
  },
  "lighting": {
    "watts_per_m2": 416.7,
    "estimated_ppfd": 1042,
    "assessment": "Excellent - suitable for flower"
  },
  "plants": {
    "count": 4,
    "area_per_plant_m2": 0.36,
    "density_assessment": "Good spacing"
  }
}

GET /v1/dry

Drying and curing calculator. Estimate dry weight yield, optimal drying duration, and get step-by-step curing instructions based on wet harvest weight, environment, and trim method.

Parameter	Type	Default	Description
wet_weightrequired	number	-	Wet harvest weight in grams
temp	number	-	Drying room temperature
humidity	number	-	Drying room humidity (%)
method	string	-	Drying method: `hang`, `rack`, or `wet_trim`

Try it

GET /v1/dry?wet_weight=500&temp=20&humidity=60

{
  "wet_weight_g": 500,
  "estimated_dry_weight_g": { "min": 100, "max": 125 },
  "dry_ratio": "4:1 to 5:1",
  "drying": {
    "duration_days": { "min": 7, "max": 14 },
    "optimal_temp": { "min": 18, "max": 21 },
    "optimal_humidity": { "min": 55, "max": 62 },
    "environment_status": "good",
    "stem_snap_test": "Ready when small stems snap, not bend"
  },
  "curing": {
    "duration_weeks": { "min": 2, "max": 8 },
    "jar_humidity_target": "58-62%",
    "burping_schedule": [
      "Week 1: Open jars 2-3 times daily for 15 min",
      "Week 2: Open jars once daily for 10 min",
      "Week 3-4: Open jars every 2-3 days",
      "Week 5+: Open once weekly"
    ]
  }
}

🔧 Utilities

GET /v1/convert

Multi-purpose unit converter for grow-related measurements. Converts between Celsius/Fahrenheit, EC/PPM (both 500 and 700 scale), PPFD/Lux, and VPD units. Provide any input and get all conversions.

Parameter	Type	Default	Description
temp	number	-	Temperature value to convert
from	string	-	Source unit for temp: `c` or `f`
ec	number	-	EC value (mS/cm) to convert to PPM
ppm	number	-	PPM value to convert to EC
ppm_scale	string	-	PPM scale: `500` or `700`
ppfd	number	-	PPFD to convert to Lux
lux	number	-	Lux to convert to PPFD
vpd	number	-	VPD value for unit info

Try it

GET /v1/convert?ec=1.5

{
  "conversions": {
    "ec": {
      "ec_ms_cm": 1.5,
      "ppm_500": 750,
      "ppm_700": 1050,
      "us_cm": 1500,
      "cf": 15
    }
  },
  "notes": {
    "ppm_500": "Hanna, Milwaukee scale (EC x 500)",
    "ppm_700": "Eutech, Truncheon scale (EC x 700)"
  }
}

GET /health

API health check endpoint. Returns current API status, version, uptime, and endpoint count. Use this to verify the API is operational before making other calls.

Parameter	Type	Default	Description
No parameters required

Try it

GET /health

{
  "status": "healthy",
  "version": "2.0.0",
  "endpoints": 18,
  "uptime": "15d 4h 22m"
}