What is the optimal CO2 level for greenhouse crops?

Most crops respond well between 800 and 1200 ppm during active photosynthesis. Tomatoes, cucumbers, and peppers are commonly enriched to 1000–1500 ppm. Going above 1500 ppm rarely improves yield and wastes gas. Maintain ambient (~400 ppm) when vents are open, as enriched air will escape.

What is air infiltration (ACH) and how do I estimate it?

Air changes per hour (ACH) measures how often the total greenhouse air volume is replaced by outside air through leaks and gaps. A tightly sealed modern glasshouse might be 0.5 ACH; a polyfilm tunnel with roll-up sides may be 1–3 ACH. Measure by logging CO2 decay after enrichment, or use 0.75 ACH as a conservative estimate for a well-maintained structure.

Why does the calculator separate "raise" flow from "maintain" flow?

Raising CO2 from ambient to target requires a one-time mass injection at the start of the dosing period. Maintaining it against continuous air infiltration requires an ongoing replenishment flow. The total flow rate combines both, averaged over the injection window.

Does this account for plant CO2 uptake?

Plant uptake is intentionally omitted because it varies widely with crop density, light intensity, and growth stage, and because CO2 enrichment is typically sized to outpace both leakage and uptake. For a conservative (higher) estimate you can increase the target ppm by 100–200 ppm to buffer for plant demand.

What unit is CO2 measured in here?

Concentrations are in parts per million by volume (ppm). Gas volume outputs are in liters per minute (L/min) and cubic feet per hour (ft³/hr). Daily totals are in liters and cubic feet. At standard conditions (20 °C, 1 atm) 1 kg CO2 ≈ 509 liters.

Can I use this for a grow tent or indoor grow room?

Yes. Enter the room volume (length × width × height) and a higher ACH (1–3) to account for exhaust fans and ducting. The calculation is identical; the inputs simply reflect a smaller, potentially leakier space.

Greenhouse CO2 Dosing Calculator

Name: Greenhouse CO2 Dosing Calculator
Availability: InStock
Author: Nham Vu

Calculate the CO2 flow rate and daily dosing volume to enrich a greenhouse to a target concentration based on volume, infiltration, and injection duration.

Greenhouse & Dosing Parameters

Unit System

Metric (m³, L/min) Imperial (ft³, ft³/hr)

Length

Width

Height

— or enter total volume directly (m³)

Ambient CO₂ (ppm)

Target CO₂ (ppm)

Air Infiltration (ACH)

Typical: 0.5–1.5 ACH

Injection Duration (hr/day)

Daylight hours only

Enter greenhouse parameters on the left and click Calculate CO₂ Dosing.

Summary

Calculate the CO2 flow rate and daily dosing volume to enrich a greenhouse to a target concentration based on volume, infiltration, and injection duration.

How it works

Enter the greenhouse internal volume (length × width × height, or total cubic meters/feet).
Set the ambient CO2 concentration (typically 400 ppm outdoors).
Set your target CO2 concentration — most crops benefit from 800–1200 ppm during daylight.
Enter the air infiltration/exchange rate (air changes per hour) — typical unventilated greenhouses are 0.5–1.5 ACH.
Enter the planned injection duration in hours per day (usually aligned with daylight hours).
The calculator derives the CO2 mass needed to raise the volume, adds the continuous replenishment flow to offset leakage, and outputs total flow rate and daily volume.

Use cases

Sizing a CO2 generator or compressed CO2 cylinder system for a hobby or commercial greenhouse.
Estimating daily CO2 gas consumption and cylinder refill frequency.
Comparing enrichment costs between propane burners and bottled CO2 at different target ppm levels.
Planning CO2 dosing schedules for seedling propagation, vegetative growth, or fruiting stages.
Checking whether an existing CO2 system can maintain target concentration in an expanded structure.
Teaching horticulture students the mass-balance approach to greenhouse gas management.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu