Memory Functions: M+, M−, MR, MC Explained
Every scientific calculator has a memory register — a single value you can store and recall during a calculation. The four memory keys control it: M+ adds to memory, M− subtracts, MR recalls, MC clears. Used well, the memory keys let you carry a value across an unrelated calculation without losing it.
What each key does
M+ — adds the current displayed value to memory. M− — subtracts the current displayed value from memory. MR (sometimes RCL) — recalls the memory value into the current expression. MC — clears the memory (sets to zero). The M indicator on the display tells you whether memory is currently non-zero. Some calculators have additional registers — A, B, C, D — for storing multiple values.
Worked example — running total
Calculate the total of three items: 12.50, 7.25, 4.80. Type 12.50, press M+ (memory is now 12.50). Type 7.25, press M+ (memory is now 19.75). Type 4.80, press M+ (memory is now 24.55). Press MR to recall the total. Press MC to reset for the next problem. Faster than typing them all into one expression for long lists.
Worked example — subtotal in a bigger formula
Compute (sin 30 + cos 60) × 1.5. Method: type sin 30 = 0.5, press M+. Type cos 60 = 0.5, press M+ (memory now 1). Press MR × 1.5 = 1.5. Or do it in one expression: (sin(30) + cos(60)) × 1.5 = 1.5. Memory is the workaround when an expression is too long to bracket cleanly.
Memory vs ANS
ANS recalls only the most recent result. Memory holds whatever you have explicitly stored, across multiple calculations. Use ANS for chained one-step work: 12 × 7 = 84, then ANS + 6 = 90. Use memory when the value needs to persist across unrelated work — for example, a constant you want to reuse, or a running total.
Clearing memory at the end
Forgetting to press MC after one problem can cause errors on the next. The M indicator stays lit as a warning — glance at the display before starting fresh. Switching off the calculator usually clears the memory, but online and some battery-backed models keep it. Make MC the last keypress when you finish a problem that used memory.
Multiple-register calculators
Mid-range and higher scientific calculators have separate STO and RCL keys with letters A through M as registers. STO A stores the current value to register A. RCL A recalls it. This lets you keep many values in play at once — useful in statistics or systems-of-equations problems where you need several constants on hand.
Frequently asked questions
What does M+ do?
M+ adds the currently displayed value to the calculator's memory register. If memory is empty (zero) and you press M+ after computing 5, memory becomes 5. Press M+ again with the value 3 displayed, and memory becomes 8. Use M+ to build a running total across many calculations.
What's the difference between MR and ANS?
MR (memory recall) retrieves the value you have explicitly stored in memory using M+ or M−. ANS retrieves the most recent calculation result automatically. ANS updates every time you press equals; memory only changes when you press M+, M−, or MC. Use ANS for short chains, memory for longer multi-step work.
How do I clear the memory?
Press MC (memory clear). Memory is reset to zero. The M indicator on the display turns off. If your calculator has multiple registers (STO A, STO B, …), you can clear each individually by storing zero in it, or use SHIFT + MC to clear all registers at once on some models.
Does turning off the calculator clear memory?
On most physical calculators, no — memory persists when off, thanks to a small backup battery. On battery-only calculators that have fully discharged, memory clears. On online or app-based calculators, memory clears when you close the tab unless the page saves it to localStorage.
Can I do more than one memory at a time?
Basic scientific calculators have one memory register. Mid-range and higher models have multiple — usually accessed via STO and RCL keys with letter names (A, B, C, D, E, F, X, Y, M). The basic M+/M−/MR/MC system always works on the default M register; the lettered registers expand the capacity.