30 is what percent of 150?

20%

Part: 30
Whole: 150
Percent: 20%

30 is 20% of 150. To find what percent one number is of another, divide the part by the whole and multiply by 100: (30 ÷ 150) × 100 = 20%. This is the reverse of "X% of Y" — useful for test scores, completion rates, and shares. Try your own numbers below.

Math

Percentage Calculator

Six quick percentage tools: what is X% of Y, what percent one number is of another, X is P% of what, percentage change, percentage difference, and adding or subtracting a percent.

What is X% of Y?

X% of Y

Percent (X)

Of (Y)

X is what percent of Y?

X ÷ Y × 100

Number (X)

Total (Y)

15%

Percentage change

From an old value to a new value

From (old)

To (new)

15% · increase

Percentage difference

Between two values (order doesn't matter)

Value A

Value B

40%

Add or subtract a percent

Base ± percent

Base value

Percent (%)

plus 92 · minus 68

X is P% of what?

X ÷ (P ÷ 100)

Number (X)

Percent (P)

How it's calculated

Each mode uses a direct formula. "What is X% of Y" computes (X / 100) × Y. "X is what % of Y" computes (X / Y) × 100, requiring Y ≠ 0. "X is P% of what" solves for the base as X / (P / 100), requiring P ≠ 0. Percentage change is ((new − old) / |old|) × 100, signed, requiring the old value ≠ 0. Percentage difference is |A − B| / ((|A| + |B|) / 2) × 100, order-independent, requiring the two values not both be zero. "Add / subtract a percent" gives base × (1 + p / 100) and base × (1 − p / 100). All formulas follow standard mathematical definitions as documented on MathIsFun.

Sources

Reviewed by the YouCalc Team · Last reviewedJune 11, 2026

Results are estimates. Verify with a professional for important decisions.

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