Science
pH and pOH Calculator
Use this pH and pOH calculator for acid-base homework when the 25 C water relationship is appropriate.
Choose the missing quantity; the calculator hides that field and solves it from the others.
Solved value
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- pH
- —
- pOH
- —
Student quick launch
Grade planning, algebra checks, and formulas students reach for most.
Study path
Use this calculator with
Follow these when you want the formula behind the answer, a short lesson, or nearby tools in the same topic.
What the ph and poh calculator solves
Use this pH and pOH calculator for acid-base homework when the 25 C water relationship is appropriate.
Formula
How to use it
- Choose the quantity you want to solve for.
- Enter the known values with consistent units.
- Check the rearranged formula, substitution, and warnings before using the result.
How to read the answer
At 25 C, lower pH means more acidic and lower pOH means more basic.
Common mistakes and edge cases
- The sum is 14 only for water at about 25 C.
- pH is logarithmic, not linear.
- Very strong acids or bases can fall outside the simple 0-14 classroom range.
Worked examples
Acidic solution
Solved value
pOH = 11
Basic solution
Solved value
pH = 9.5
Frequently asked questions
Can the ph and poh calculator solve for a missing variable?+
Yes. Use the solve-for control to hide the missing value, then enter the other known values with compatible units.
Why do the units matter?+
Formula calculators assume the entered values are already in matching units. Convert first when your measurements use mixed systems.
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Last updated: May 15, 2026