⚗️ Interactive pH Calculator
Bidirectional pH ↔ mV Converter with Temperature Compensation
Calculate pH from millivolts (mV) and vice versa using the Nernst equation with automatic temperature adjustment
🧮 pH Calculator
📐 Nernst Equation & Formulas
Where:
• E_ref = Reference electrode potential (mV)
• E_meas = Measured electrode potential (mV)
• S = Slope (temperature-dependent)
• At 25°C: S = 59.16 mV/pH
• At 0°C: S = 54.21 mV/pH
• At 50°C: S = 63.11 mV/pH
Assuming 0 mV reference at pH 7 (neutral point)
Temperature-compensated conversion from electrode potential
📚 Understanding pH and mV Relationship
🔬 What is pH?
pH is the logarithmic measure of hydrogen ion (H⁺) concentration. It ranges from 0 to 14, where 7 is neutral, values below 7 are acidic, and values above 7 are alkaline.
⚡ What are millivolts (mV)?
Millivolts represent the electrochemical potential difference between the glass electrode and the reference electrode. This is the raw signal that gets converted to pH.
🌡️ Temperature Compensation
Temperature significantly affects electrode response. The slope of the pH-mV relationship changes by 0.198 mV/pH per degree Celsius. Always compensate for accurate results.
🧲 Nernst Equation
The Nernst equation describes the electrochemical potential of an electrode at any given temperature. It’s the mathematical foundation for all pH measurements.
📊 Electrode Slope
The ideal slope is 59.16 mV/pH at 25°C. Electrodes typically achieve 95-105% of this value. Lower slopes indicate electrode aging.
🔄 Bidirectional Conversion
You can convert pH to mV OR mV to pH depending on your measurement. Enter either value and click the corresponding button to calculate the other.
📋 Reference Values at 25°C
Standard pH Buffers & Their mV Values
| Buffer Type | pH Value | Typical mV (25°C) | Application |
|---|---|---|---|
| Acidic Buffer | 4.00 | +177 mV | Low pH calibration |
| Neutral Buffer | 7.00 | 0 mV | Reference point |
| Alkaline Buffer | 10.01 | -177 mV | High pH calibration |
| Very Acidic | 2.00 | +295 mV | Extreme acidity |
| Very Alkaline | 12.00 | -295 mV | Extreme alkalinity |
Temperature Effects on Slope
| Temperature (°C) | Slope (mV/pH) | Change from 25°C |
|---|---|---|
| 0 | 54.21 | -4.95 mV/pH |
| 10 | 56.20 | -2.96 mV/pH |
| 25 | 59.16 | 0 mV/pH (reference) |
| 40 | 62.13 | +2.97 mV/pH |
| 60 | 66.08 | +6.92 mV/pH |
| 80 | 70.02 | +10.86 mV/pH |
🚀 How to Use This Calculator
Step-by-Step Guide:
- Set Temperature: Adjust the temperature slider to match your process or measurement environment. The default is 25°C, which is the standard reference temperature.
- Choose Conversion Direction: Decide whether you want to convert from pH to mV or from mV to pH.
- Enter Input Value: Input either the pH value (0-14) or the mV value (-414 to +414).
- Click Calculate: Press the appropriate “Calculate” button to perform the conversion.
- Review Results: The calculator will display the converted value along with the temperature-adjusted slope and other useful parameters.
- Reset if Needed: Use the “Reset All” button to clear all inputs and start a new calculation.
• Lab Analysis: Convert electrode readings to pH for water quality testing
• Industrial Control: Monitor pH in chemical reactors and adjust acid/base dosing
• Electrode Calibration: Verify electrode performance by comparing calculated vs. actual mV
• Temperature Correction: Adjust pH measurements when process temperature changes
• Troubleshooting: Identify sensor issues by checking mV-pH relationships