Percentage calculator

Percentage calculator has four modes. What is A% of B multiplies A divided by 100 by B. Percentage change from A to B subtracts A from B, divides by the absolute value of A, and multiplies by 100. A is what percentage of B divides A by B and multiplies by 100. Increase or decrease B by A% applies both factors and displays both adjusted values. The labels reuse A and B, but their roles change with the selected equation.

Write the question in words before entering numbers. In 20% of 150, A is 20 and B is 150. In change from 150 to 180, A is the starting 150 and B is the ending 180. In 30 is what percentage of 120, A is the part 30 and B is the total 120. Reversing values answers a different question.

The mode defaults to What is A% of B. Switching modes does not transform existing inputs, so review both values after changing the selector. The two fields accept any finite JavaScript number and do not enforce domain-specific ranges. Negative values and percentages over 100 are calculated mathematically even when they make no sense for a particular business measure.

For 20% of 150, select the default mode, enter 20 as Value A, and enter 150 as Value B. The calculation is 20 divided by 100 multiplied by 150, which equals 30. The result displays 30.00 and then the text 20% of 150.

Decimals work the same way. For 7.5% of 240, the unrounded result is 18, so the page shows 18.00. A value such as 12.345% of 19.99 may contain more decimal places internally, but the result is formatted to two decimal places with toFixed(2). That display rounding may differ from currency rules applied elsewhere.

This mode does not add or subtract the percentage from B. It returns only the portion. Choose Increase or decrease B by A% when you need both adjusted values. Use Discount calculator when the result needs sale-price labels, or VAT calculator when the calculation must distinguish inclusive and exclusive tax.

Percentage change uses ((B minus A) divided by the absolute value of A) multiplied by 100. From 100 to 125, the difference is 25, the denominator is 100, and the result is 25.00% increase. From 100 to 75, the computed result is -25.00%, and the page appends decrease.

The absolute denominator gives defined behavior for negative starts. From -100 to -50, the difference is 50 and the denominator is 100, so the output is 50.00% increase. From -100 to -150, it is -50.00% decrease. Whether those labels describe a meaningful improvement or decline depends on the metric; the calculator only compares numerical direction.

A starting value of zero is explicitly rejected because percentage change from zero would require division by zero. When a report needs to describe a move from zero, use absolute change, a new-versus-none label, or another convention defined by that report. Do not replace zero with a tiny number merely to force a large percentage.

A is what percentage of B computes A divided by B times 100. Enter 30 and 120 to receive 25.00%, followed by 30 is 25.00% of 120. The calculation supports parts larger than totals, so 150 out of 120 returns 125.00%. That may be correct for attainment above a target but impossible for categories that must partition one fixed whole.

The total B cannot be zero and the page rejects it. A can be zero, producing 0.00% when B is nonzero. Negative totals are accepted by the number parser and produce signed results. Before using such an output, confirm that a signed denominator is valid for the subject rather than an input mistake.

Completion rates, defect shares, and survey proportions often require counts drawn from the same population. This calculator does not verify that relationship, remove duplicates, weight observations, or handle missing data. Prepare a valid numerator and denominator first, then use the ratio mode for arithmetic.

Every numeric percentage result is displayed with exactly two digits after the decimal point. JavaScript performs the arithmetic with binary floating-point numbers before toFixed(2) formats the string. Values near a half-cent style boundary can round in ways that differ from a decimal accounting system. The tool does not expose extra precision or a rounding-mode selector.

Do not recompute later stages from a rounded percentage when the underlying values are available. For example, a displayed ratio of 33.33% may represent one third. Multiplying 33.33% by another total can drift from using the original numerator and denominator. Keep source values in analytical work and use the formatted percentage for presentation.

The formula line prints entered A and B values as JavaScript string representations. It is an explanation, not a formal audit record with locale-specific number formatting. Copy the source inputs and mode alongside consequential results. Spreadsheet or accounting systems may require decimal types and explicit rounding policies.

Many percentage errors come from choosing the wrong base. A rise from 80 to 100 is 25% because the 20 increase is divided by the starting 80. A fall from 100 back to 80 is 20% because the 20 decrease is divided by 100. Equal absolute moves do not necessarily have equal percentage changes.

Successive changes also do not simply cancel. Increasing 100 by 20% gives 120. Decreasing 120 by 20% gives 96, not 100, because the second percentage uses a different base. Calculate each stage from its actual starting value, or use a compound factor when modeling several periods.

A percentage point change is different from a percent change. Moving a rate from 20% to 25% is an increase of 5 percentage points and a relative increase of 25%. This page can compute the relative change by entering 20 and 25 in change mode, but it does not label percentage-point differences. State which measure you report.

The calculator reports a valid-number error when a required value does not convert to a finite number. Blank number inputs can be interpreted as zero by JavaScript, so do not rely on an empty field to trigger validation. Enter both intended values explicitly. Reset clears inputs, result, error, and returns the mode to its default.

If change mode says decrease beside a negative percentage, that is the implemented display: the signed value is retained and the direction word is appended. If a reporting style expects 25.00% decrease without a minus sign, reformat carefully outside the tool while preserving the underlying calculation. Do not change both sign and label in a way that reverses meaning.

If the answer is 100 times too large or small, check whether A was entered as 20 or 0.20. This page interprets 20 as 20 percent in the percentage-of mode. Ratio and change modes multiply their quotient by 100 automatically. Enter raw values there, not numbers already converted to percentages unless those percentages are themselves the quantities being compared.

Discount calculator applies a rate to an original price and formats saving and sale price as USD. VAT calculator distinguishes adding tax to a net value from extracting included tax from a gross value. Compound interest and Loan calculators apply monthly rate formulas across time. Percentage calculator does none of that context-specific modeling.

Use this page for a direct percentage equation when you already know which values belong in the formula. Use a specialized page when labels, sequence, contribution timing, or inclusive pricing change the mathematics. A 20% VAT included in 120 is not found by taking 20% of 120; removing included VAT divides by 1.20.

Verify consequential outputs in the system that owns the source data. Percentages can look precise while hiding bad denominators, inconsistent periods, or rounded inputs. The calculator confirms arithmetic under its three equations, not the validity of a business, scientific, medical, tax, or financial interpretation.

Negative numbers are valid arithmetic inputs but need contextual rules. A ratio of -20 to 100 is -20%, while -20 divided by -100 is 20%. Change mode uses the absolute starting value, so direction comes from B minus A rather than the denominator sign. Review the formula line whenever signed data represents debt, temperature, profit, or balance changes.

Crossing zero is especially easy to misdescribe. A move from -10 to 10 produces a 200% increase under the implemented formula. Some reports avoid relative percentages across zero because the interpretation is unstable. Choose an absolute difference or a domain-approved measure when that convention fits better.

The calculator does not label good and bad outcomes. An increase in errors and an increase in revenue receive the same direction word. Add the metric name, period, and base to every reported percentage.

For percentage-of mode, divide the result by B and multiply by 100 to recover A when B is nonzero. For ratio mode, multiply B by the displayed percentage divided by 100 and compare with A, allowing for two-decimal rounding. These checks catch reversed fields.

For change mode, calculate the absolute difference first and compare it with the starting magnitude. From 80 to 92, difference is 12 and 12 divided by 80 is 0.15, so the result should be 15.00% increase. A spreadsheet using the same equation offers a second check for important work.

Keep full source precision through the check. A displayed 14.29% may come from one seventh, and reversing the rounded percentage will not reproduce the exact numerator.

Copy includes the formatted answer and explanation but not the selected menu state as a separate field. Preserve the wording of the question with A and B so the same two numbers are not later interpreted under another mode.