What model does this calculator use?

For unbuffered solutions it uses the strong-acid/strong-base model: [H+] and [OH-] are computed from each pH, the difference in H+ (or OH-) moles across the volume is found, and that mole difference is divided by the reagent concentration to get the volume needed. This is accurate for dilute, unbuffered solutions.

Why does a small pH change near neutral require more reagent?

pH is a logarithmic scale, so a change of 1 unit represents a 10x change in [H+]. Near neutral (pH 7) the absolute [H+] and [OH-] concentrations are very low, so small shifts require proportionally more reagent to overcome the near-neutral buffering effect of water itself.

Does this work for buffered solutions?

This tool models unbuffered (or weakly buffered) solutions. Buffered solutions resist pH change, so the actual reagent required will be higher. Use the Henderson-Hasselbalch calculator to model buffered systems.

What concentration unit should I use for the reagent?

Enter the molar concentration in mol/L (M). For example, household muriatic acid is roughly 10–12 M HCl, and a standard lab NaOH solution is often 1 M or 0.1 M.

Can I use this for any acid or base, not just HCl and NaOH?

Yes — the calculation depends only on the moles of H+ or OH- provided per mole of reagent. For monoprotic strong acids (HCl, HNO3, HBr) and monobasic strong bases (NaOH, KOH, LiOH), one mole of reagent gives one mole of H+ or OH-. Enter the corresponding molar concentration and the result applies directly.

pH Control Calculator

Name: pH Control Calculator
Availability: InStock
Author: Nham Vu

Enter your current pH, target pH, solution volume, and reagent concentration to find how much acid or base to add.

Solution Parameters

Current pH

Range: 0 – 14

Target pH

Solution Volume

Reagent

Strong acid (HCl) Strong base (NaOH)

Adding acid lowers pH.

Reagent Concentration (mol/L)

Molar concentration of your acid or base reagent.

Quick Presets

Dosing Results

Fill in the parameters above, then click Calculate.

How the Calculation Works

Step 1 — Convert pH

[H⁺] = 10^−pH

[OH⁻] = 10^pH−14

Step 2 — Mole Deficit

Δmol = |[H⁺]_target − [H⁺]_current| × V

(V in liters)

Step 3 — Reagent Volume

V_reagent = Δmol / C_reagent

Divide by molar concentration

Valid for dilute, unbuffered (or weakly buffered) solutions with strong monoprotic acid or monobasic strong base reagents. For buffered systems, use the Henderson-Hasselbalch calculator instead.

Summary

Enter your current pH, target pH, solution volume, and reagent concentration to find how much acid or base to add.

How it works

Enter the current pH of your solution.
Enter the target pH you want to reach.
Enter the total volume of solution (in liters or mL).
Select whether you are adding a strong acid (HCl) or strong base (NaOH) to adjust the pH.
Enter the molar concentration of your reagent.
Click Calculate to see the volume and moles of reagent needed.

Use cases

Determine how much HCl to add to lower pool or tank water pH.
Calculate NaOH dose needed to neutralize an acidic waste stream.
Prepare laboratory solutions at a precise target pH.
Estimate reagent volumes for water treatment and process control.
Verify manual pH adjustment calculations in industrial settings.
Support titration experiment planning by pre-calculating reagent needs.

Frequently Asked Questions

Last updated: 2026-06-18 · Reviewed by Nham Vu