Your calculator workspace.
Environment readings, water measurements, electricity costs, and unit conversions. Inputs clear on reload; export your water log before leaving.
Your environment
Leave blank to assume the leaf and air are the same temperature.
Your reference range
The starting range is an editable comparison example, not a universal target or a growth-stage recommendation.
A clearer climate reading.
Saved readings and history are being built for iPhone and Android. Store downloads aren’t available yet.
What this calculates
VPD compares saturation vapor pressure with the actual vapor pressure of the air. It is an estimate based on your inputs, not a measured plant response.
eₛ(T) = 0.6108 × exp(17.27T / (T + 237.3))Leaf VPD = eₛ(Tleaf) − eₛ(Tair) × RH / 100Temperatures are converted to Celsius internally. Results are in kilopascals; the temperature formula uses FAO-56 equation 11. Growth targets depend on the crop and conditions, so this first calculator lets you set your own reference range.
Water readings & scales
Convert your meter’s display scale and keep pH, conductivity, water volumes, and sample notes together.
EC / PPM converter
Match your meter’s scale1,000 µS/cm
These are different displays of the same conductivity reading. PPM is an estimate based on the selected factor; it does not identify individual substances or establish water safety. This tool does not temperature-correct readings.
Session log 0
Export before leaving. This log is kept only on this page and clears on reload. Downloads stay wherever you save them.
What the scale conversion means
1 mS/cm = 1,000 µS/cm. Estimated TDS in ppm = EC in mS/cm × 500 or × 700. To convert from an estimated PPM display, divide by its matching factor. Changing scales changes the number, not the sample.
pH is recorded separately. EC and pH cannot be converted into one another here. Check the unit and scale in your meter’s documentation.
Source: Hanna Instruments, TDS conversion factorsElectricity & expenses
Enter actual equipment power, its daily schedule, and the rate on your utility bill. Starting values are examples.
45.6 kWh over 30 days
$0.24 per day
90 days · 136.8 kWh
Rate & forecast
Use your bill’s energy rate$0.16 is an example, not a verified national or local average.
The same daily schedule is repeated for this period.
Your equipment
Duty is the percentage of scheduled time the device is actually on. For example, 50% of a 24-hour schedule means 12 hours of powered operation.
Additional expenses
Enter each expense once for the selected 90-day period. These amounts are added to the period’s electricity estimate; they are not multiplied by the number of days.
$21.89 electricity + $0.00 entered expenses
How this estimate works
Daily kWh = watts while on × scheduled hours × duty percentage ÷ 100 × quantity ÷ 1,000. Energy cost = kWh × your rate. The monthly card always means 30 days, not a calendar billing month.
Use measured power when available. Nameplate wattage can overstate typical use. If you enter average watts measured across the whole schedule, set duty to 100% so it is not counted twice. This simple estimate excludes standby consumption, fixed fees, taxes, demand charges, and time-of-use rates.
Source: U.S. Energy Information AdministrationUnit conversions
Convert volume, length, area, weight, and temperature. Gallon types and fluid ounces are labeled explicitly.
5 US gal
Shown to six decimal places. Full precision is used when swapping units.
Conversion definitions
1 US liquid gallon = 3.785411784 liters. 1 Imperial gallon = 4.54609 liters. 1 foot = 0.3048 meters. 1 pound = 453.59237 grams. 1 ounce (weight) = 1/16 pound.
°C = (°F − 32) × 5/9. Kelvin = °C + 273.15. Constants are retained at full precision; displayed measurements are rounded.
Source: NIST Handbook 44, Appendix C