Calculator Memory Buttons: MC, MR, MS, M+ and M−

Updated 5 November 2026 · Standard formula, shown below

On most calculators, MC clears the stored memory, MR recalls its value, MS stores the displayed value, M+ adds the display to memory, and M− subtracts it. Together, these buttons let you keep a running total or reuse a number without copying it down; the exact labels and behavior can vary slightly by calculator.

What the memory buttons mean

MC — Memory Clear: Erases the number held in memory. It does not usually clear the current display or reset every calculator setting.
MR — Memory Recall: Places the stored number on the display so you can use it in a calculation. On many calculators, recalling a value leaves the memory unchanged.
MS — Memory Store: Replaces the stored value with the number currently shown on the display.
M+ — Memory Add: Adds the displayed number to the stored value and saves the new total.
M− — Memory Subtract: Subtracts the displayed number from the stored value and saves the result.

These are distinct commands, not interchangeable versions of a general “memory” key. In particular, MS replaces what was stored, while M+ and M− update it. A calculator may show an M indicator when memory contains a value; that indicator is a status signal, not an extra memory button.

How calculator memory works

Think of memory as one small, separate storage space for a number. The screen shows the number you are currently entering or calculating, while the memory value stays in the background until you change it or clear it. Pressing M+ or M− combines the displayed value with that background value.

Suppose memory currently holds 12. If the display shows 5 and you press M+, memory becomes 17. If you then show 3 and press M−, memory becomes 14. Pressing MR displays 14. The sequence can be summarized as:

MS: memory becomes the displayed number.
M+: memory becomes memory plus the displayed number.
M−: memory becomes memory minus the displayed number.
MR: display becomes the stored number.
MC: memory is cleared.

When memory has been cleared, many calculators treat its value as zero, so the first M+ adds to zero. However, display indicators and the precise effect of clearing memory are model-dependent. Check the calculator’s instructions if a sequence behaves differently than expected.

A practical example: totaling several amounts

Memory is useful when you want to add numbers that are not next to each other in a calculation, or when you need to reuse a subtotal. For example, to total three amounts—18.75, 6.40, and 12.00—without writing down each running total:

Enter 18.75 and press MS. Memory now holds 18.75.
Enter 6.40 and press M+. Memory now holds 25.15.
Enter 12.00 and press M+. Memory now holds 37.15.
Press MR to display the total.
Press MC when you are finished and want to remove the stored total.

You could also use M+ for the first amount if memory is known to be clear. Using MS at the start is often safer because it explicitly replaces any old value. If you forget to clear old memory and begin with M+, the previous value may be included in your total.

Memory versus the display and other calculator features

Calculator memory is separate from the number on the screen. A clear-entry key, often labeled CE, generally removes the number being entered; an all-clear key, often labeled C or AC, generally clears the current calculation. Neither should be assumed to erase stored memory. Conversely, MC usually clears memory without necessarily clearing the screen.

Some calculators have more than one memory register, memory-recall shortcuts, or a dedicated MRC key that combines memory recall and clear functions. Others use an on-screen memory list or store several values. These variations mean that the familiar MC, MR, MS, M+ and M− definitions are a useful baseline, but the manual or help screen is the authority for a particular device.

Memory is also different from a calculator’s “Ans” or previous-answer feature. An answer feature typically recalls the result of the last calculation automatically or through a separate key. Memory is a value you deliberately store or update, and it can remain available across several calculations.

Common mistakes and ways to avoid them

Adding to an old value: M+ does not necessarily start a fresh total. Press MC first, or press MS with the first number to replace whatever was stored.
Using MS when you mean M+: MS overwrites memory. If you press it for each item in a running total, only the latest item may remain.
Assuming AC clears memory: On many models it does not. Use MC when the goal is to clear stored memory.
Forgetting what is stored: Press MR to inspect the memory value before continuing. Remember that this can change the display, so note or finish any current entry first.
Expecting unlimited precision: Memory stores a numerical value subject to the calculator’s precision and rounding behavior. A displayed result may show fewer digits than the value used internally.

If a total looks wrong, recall memory and check its value before starting over. Then clear it or deliberately replace it with MS. This simple reset-and-store routine prevents most accidental carryovers.

When memory buttons are useful

Memory can help with repeated arithmetic, such as summing scattered line items, combining subtotals, or holding a constant while you work through separate calculations. It can also reduce transcription errors when you would otherwise copy a result from the display onto paper and type it again.

For long lists, complicated formulas, or work that must be reviewed later, a written calculation, spreadsheet, or calculator with multiple named registers may be clearer. A single memory register has no label: after several operations, it can be difficult to remember whether it contains a subtotal, a starting value, or something left over from earlier.

Frequently Asked Questions

What does M mean on a calculator?
The M indicator usually means that a value is stored in calculator memory. It is generally a status symbol rather than a command; the stored value can often be displayed with MR.

What is the difference between MS and M+?
MS replaces the memory value with the number on the display. M+ adds the displayed number to the value already in memory.

Does AC clear calculator memory?
Not necessarily. AC often clears the current calculation or display, while MC is the memory-clear command. Behavior varies by model, so check its instructions.

How do I clear memory on a calculator?
Press MC, usually labeled Memory Clear. If your calculator uses a combined key or menu instead, follow its displayed instructions or manual.

Can I use M− to make a negative number?
M− subtracts the displayed value from the stored value; it is not always the same as entering a negative number on the screen. Use the sign-change or negative-number key when you need a negative displayed value.

Why does my calculator show M after I cleared the screen?
Clearing the display may leave the stored memory untouched. Recall it with MR, or press MC to clear the memory register.

Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.