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Percent Decrease Calculator

Percent decrease is a drop divided by the level it fell from. The denominator decides everything: 120 to 90 is a fall of 25.00%, and the same 30 measured against 90 gives 33.3333%, which answers a different question entirely.

Percent decrease

25.00%

Absolute decrease
30
Share of the original that remains
75.00%
The same drop divided by the new value (the wrong way round)
33.33%

Values update as you type. This calculator covers the single scenario its formula assumes — see Common Mistakes for what it leaves out.

The formula this calculator uses

Percent Decrease = (Original Value - New Value) / Original Value x 100

V0
Original value — where the quantity stood before the fall
V1
New value — the lower figure after the decrease
V0 - V1
Absolute drop, before it is scaled into a rate
V1 / V0
Share that remains — 0.75 here, the mirror of a 25.00% decrease

How to check the result by hand

  1. 1

    Fix the original value before anything else

    The original is the figure the change happened to, in time order, not the larger of the two and not the one nearest to hand. For a fall from 120 to 90 the original is 120, and it stays the divisor for every step that follows.

  2. 2

    Subtract to get the absolute drop

    120 - 90 = 30. Keep this number visible, because it is the one part of the answer that survives even when the percentage itself is not meaningful, such as when the original was zero.

  3. 3

    Divide the drop by the original value

    30 ÷ 120 = 0.25. Dividing by 90 instead produces 33.3333%, which is the rise needed to get back rather than the fall that occurred, so check which figure sits underneath the bar.

  4. 4

    Multiply by 100 and state the direction

    0.25 x 100 = 25.00% decrease. Naming the direction in words is not decoration: a bare percentage invites the reader to attach it to whichever direction they were expecting.

  5. 5

    Cross-check with the share that remains

    90 ÷ 120 = 0.75. A 25.00% decrease must leave 75% of the original standing, so the decrease and the remaining share add to 1. If they do not, the division used the wrong base.

For worked examples, common mistakes and the limits of this formula, read the full How To Calculate Percent Decrease page.