Plant Care
- • Climate Control & VPD16
- • Disease & Pest Management14
- • Nutrient Solutions & EC34
- • Plant Health Monitoring7
Inputs
12 parameters · live recalculation on every change
L
1L
10L default
100L
L
0.1L
2L default
20L
%
5%
20% default
50%
Pro Settings — Lab Controls
°C
10°C
20°C default
35°C
KPA
0.2kPa
1kPa default
3kPa
MS/CM
0.5mS/cm
1.8mS/cm default
4mS/cm
Advanced Settings — Deterministic Corrections
%
20%
75% default
90%
%
5%
15% default
40%
G/CM³
0.05g/cm³
0.2g/cm³ default
1.5g/cm³
%
30%
85% default
95%
Insight band · live
From field capacity to plant-available water
The water a root zone can actually hand the plant is field capacity minus the share bound at wilting point.
- Field capacity 7.50 7.50 L
- − Unavailable 1.50 6.00 L
- Plant-available 6.00 6.00 L
Moisture: 80 %
WHC: 60 %
Running total after each term — the final net matches the headline reading in the result card, kept in sync live.
Deterministic model
12 inputs · 10 outputs
Runs 100% in your browser
This is a deterministic model: the same inputs always produce the same outputs, calculated entirely in your browser with nothing sent to any server. It is a planning aid — not a quote, not a dosing instruction, and not a yield forecast. Treat every line as a working estimate and validate it against your own prices and measurements.
It models one system: A substrate moisture calculator that reads your pot like a water bank: field capacity per medium (coco 75%, rockwool 80%, soil 45%, perlite 35%, clay 50%), a wilting point below it (coco 15%, rockwool 10%, soil 15%, perlite 5%, clay 10%), and the dryback you actually steer — moisture = 100 − dryback, where dryback is your target lifted by VPD. It then prices the litres of water holding this gives you, the runoff your shot genuinely makes, the air-filled porosity your roots breathe, and the EC drift the substrate stacks, closed in a green—yellow—red safety band across moisture, aeration and water holding.
What the Substrate Moisture Calculator — Dryback & Water Holding Blueprint returns
The engine computes 10 outputs from your 12 inputs. The headline number is Substrate Moisture (%), alongside Dryback Actual, Water Holding Capacity, Air-Filled Porosity. Every output updates live as you change a parameter.
What it does not do
Outputs depend on the inputs and assumptions shown here. Confirm relevant measurements and local conditions before acting.
STEP 01
Pick the medium and container size
STEP 02
Set the irrigation shot
STEP 03
Slide the dryback target
STEP 04
Read moisture as 100 minus dryback
STEP 05
Check the air the roots breathe
STEP 06
Price the salt the no-runoff shot stacks
DB_{actual}=DB_{target}\cdot f_{VPD}
Actual dryback — target × the VPD factor, so dry air pulls more
M_{substrate}=100-DB_{actual}
Substrate moisture — what your sensor reads
WHC=FC-WP
Water holding capacity — field capacity minus wilting point
FC_{L}=V_{container}\cdot\frac{FC}{100}
Field capacity in litres — the top of the water bank
WP_{L}=V_{container}\cdot\frac{WP}{100}
Wilting point in litres — the floor of the bank
Runoff=\max\left(0,\;I_{shot}-\left(FC_{L}-M_{current}\right)\right)
Runoff — the shot only drains after the storage gap is full
AFP=P_{porosity}-M_{actual}
Air-filled porosity — pore space minus the water sitting in it
\Delta EC=EC_{substrate}\cdot\left(1-\frac{Runoff}{V_{container}}\right)\cdot0.05
EC drift — salt stacking the moment runoff stops
Field capacity by medium — same locked table as the irrigation timer: coco 75%, rockwool 80%, soil 45%, perlite 35%, clay 50%.
Wilting point by medium: coco 15%, rockwool 10%, soil 15%, perlite 5%, clay 10% — the floor of the bank.
Water holding capacity = FC − WP: coco 60%, rockwool 70%, soil 30%, perlite 30%, clay 40%.
Moisture = 100 − dryback actual, so a 20% target at VPD 1.0 reads 80% on the sensor.
Air-filled porosity = porosity − moisture; roots need both, and 15–30% AFP is the air band to land in.
Runoff is honest water accounting: it only happens once the shot fills the gap between storage left and field capacity. Safety bands — moisture 50–70% GREEN · AFP 15–30% GREEN · WHC 30–60%.
- Field capacity by medium: coco 75%, rockwool 80%, soil 45%, perlite 35%, clay 50% — the archived irrigation-timer engine held a per-medium water-holding table so shot size followed the medium; the locked table here is that bank scaled to litres in your container.
- Wilting point by medium: coco 15%, rockwool 10%, soil 15%, perlite 5%, clay 10% — the floor of the usable bank; WHC = field capacity − wilting point gives coco 60%, rockwool 70%, soil 30%, perlite 30%, clay 40%.
- Moisture: moisture = 100 − dryback_actual; dryback_actual = target × VPD_factor (0.8 kPa → 0.8, 1.0 → 1.0, 1.4 → 1.3) — the archived dryback discipline read the medias wetness through the sensor and steered off the transpired gap, so a 20% target at neutral VPD reads the sensor at 80%.
- Runoff: runoff = max(0, irrigation − (field capacity L − current moisture L)) — the archived drip guide tuned events so the shot drained after the pot was full; this arm is honest water accounting, no runoff until the storage gap is filled.
- Air-filled porosity: AFP = porosity − moisture_actual — the archived irrigation guide rated every medium by air volume alongside WHC (coco 60% water / 25% air, rockwool 62/30); roots need both, and 15–30% AFP is the air band to land in.
- Safety and EC: green moisture 50–70%, AFP 15–30%, WHC 30–60%, red under 40% or over 80% moisture; EC drift = substrate EC × (1 − runoff ÷ container) × 0.05 — no runoff means every fed ion stays, exactly the salt trap the archived steering discipline warned against.
This model combines the earlier Substrate-moisture-calculator, Water-holding-capacity-calculator, Dryback-calculator models.
Q1: substrate moisture calculator hydroponics ▾
The substrate moisture calculator reads moisture as 100 minus your actual dryback — a 20% dryback target at steady VPD reads 80% on the sensor — scaled by medium field capacity (coco 75%, rockwool 80%, soil 45%). It reports moisture, air-filled porosity, water holding capacity, runoff and EC drift in one safety band.
Q2: dryback calculator hydroponics ▾
The dryback calculator prices the percent of available water transpired between irrigation events. Actual dryback = target × the VPD factor — 1.3 at 1.4 kPa pulls more from your 10–30% working band toward the generative red edge than 0.8 in gentle air — exactly the steering the archived irrigation engine leaned on.
Q3: water holding capacity calculator substrate ▾
Water holding capacity is field capacity minus wilting point: coco 75−15 = 60%, rockwool 80−10 = 70%, soil 45−15 = 30%, perlite 35−5 = 30%, clay 50−10 = 40%. The calculator scales that percent to litres in your container so the bank is something you can actually pour.
Q4: how to measure substrate moisture ▾
Read the substrate sensor and compare against the moisture this calculator derives from your dryback target: moisture = 100 − dryback actual. A 20% target at VPD 1.0 reads 80%; a 30% generative dryback reads 70%. Stay inside the 50–70% green band and trust the sensor, not your finger.
Q5: air filled porosity calculator ▾
Air-filled porosity (AFP) is total porosity minus the moisture the medium is holding right now — AFP = porosity − moisture. Roots drown when AFP collapses toward 10% and starve for water above 40%; the ideal air band is 15–30%, which this calculator reports alongside moisture in one safety view.
Q6: what is field capacity ▾
Field capacity is how much water a medium holds against gravity after a full drain — the top of the usable bank. Coco holds 75% of its volume, rockwool 80%, soil 45%, perlite 35%, clay 50%. Below the wilting point (coco 15%, rockwool 10%) the plant can no longer pull that water, so the gap between the two is what really feeds the crop.