# Calibration solution

> A calibration solution is a standard liquid of known pH or EC used to calibrate meters, such as pH 4.01, 7.00 and 10.01 buffers or 1.413 mS/cm EC standard.

- Canonical: https://genetixbay.com/knowledge/glossary/calibration-solution.html
- Also written: calibration fluid, buffer solution pH 7, pH 4 buffer, 1413 solution, EC standard, cal solution
- Glossary category: pH, EC and water · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

A calibration solution is a reference liquid with a certified value at a stated temperature, usually 25 °C. [pH](https://genetixbay.com/knowledge/glossary/ph.md) buffers are commonly 4.01, 7.00 and 10.01. [EC](https://genetixbay.com/knowledge/glossary/ec.md) standards include 1,413 µS/cm (1.413 [mS/cm](https://genetixbay.com/knowledge/glossary/ms-cm.md)), a potassium [chloride](https://genetixbay.com/knowledge/glossary/chloride-nutrient.md) solution that sits in the range of most nutrient solutions, plus lower and higher standards for water and strong solutions.

## In practice

Use fresh solution for each calibration: pour a small amount into a clean cup, calibrate, then discard it. Never dip the probe into the stock bottle or pour used solution back. Check the expiry date; once opened, buffers drift as they absorb CO2 (the pH 10 buffer is most sensitive) and as dirty probes contaminate them. Single-use sachets avoid this.

Rinse the probe with distilled or [RO water](https://genetixbay.com/knowledge/glossary/ro-water.md) between solutions and blot, do not wipe, the glass bulb. Let solution and probe reach room temperature before calibrating, or use a meter with [automatic temperature compensation](https://genetixbay.com/knowledge/glossary/atc.md).

## Don't confuse with

- **Storage solution**: usually 3 M potassium chloride, used to keep pH probes hydrated; it is not a calibration standard.
- **pH Up and pH Down**: adjust solutions; they are not references.

## Related terms

[Two-point calibration](https://genetixbay.com/knowledge/glossary/two-point-calibration.md), [pH meter](https://genetixbay.com/knowledge/glossary/ph-meter.md), [EC meter](https://genetixbay.com/knowledge/glossary/ec-meter.md), [pH buffer](https://genetixbay.com/knowledge/glossary/ph-buffer.md)

## Read more

- [pH and EC meter calibration: buffers, slope, storage and when to replace a probe](https://genetixbay.com/knowledge/ph-ec/meter-calibration.md)