How do you calculate a percentage?

To find X% of Y, multiply Y by X divided by 100 so 15% of 80 is 80 × 0.15 = 12. To find what percentage X is of Y, divide X by Y and multiply by 100. To find percentage change, subtract the original value from the new one, divide by the original, and multiply by 100.

What's the difference between percentage points and percent?

Percentage points measure the arithmetic difference between two percentages; percent measures relative change. A mortgage rate moving from 4% to 5% has risen by one percentage point but that is a 25% increase. Both are correct and they are not interchangeable.

Why isn't a 50% loss cancelled out by a 50% gain?

Because the base changes. A 50% fall from $100 leaves $50, and a 50% gain on $50 is only $75. To get back to $100 you need a 100% increase. A 20% loss needs a 25% gain, and a 75% loss needs 300%.

Is 20% off then 10% off the same as 30% off?

No. The second discount applies to the already reduced price, so the combined discount is 28%, not 30%. On $100 that is $72 rather than $70. For two successive discounts, combined = 1 less (1 less a) × (1 less b).

How do I find the original price after a discount?

Divide rather than add. If an item is $80 after 20% off, the $80 represents 80% of the original so $80 ÷ 0.80 = $100. Adding 20% back to $80 gives $96, which is wrong.

How do I remove sales tax from a total?

Divide by 1 plus the tax rate. A $113 total including 13% Ontario HST gives a pre tax price of $113 ÷ 1.13 = $100. Subtracting 13% from $113 gives $98.31, which is incorrect.

How much should I tip in Canada?

15 to 20% of the pre tax subtotal at sit down restaurants 15% is adequate, 18% has become the norm, and 20%+ for excellent service. Around 10 to 15% for taxis and rideshare, and $2 to $5 per night for hotel housekeeping. Counter service and takeout generally aren't expected to be tipped.

Can I use the tax line on my bill to calculate a tip?

It depends on your province. In New Brunswick, Newfoundland and Labrador and PEI, the 15% HST is exactly a 15% tip. In Quebec, 14.975% is effectively the same. In Ontario the 13% HST is slightly under standard. In Alberta and the territories the 5% GST is nowhere close doubling it gives only 10%.

What's the difference between markup and margin?

Markup is profit as a percentage of cost; margin is profit as a percentage of the selling price. An item costing $60 and selling for $100 has a 66.7% markup but a 40% margin same $40 profit, different base.

How do I calculate percentages in my head?

Start with 10% by moving the decimal one place left, then build from there 5% is half of that, 20% is double, and 15% is 10% plus 5%. It also helps to know that X% of Y equals Y% of X, so 18% of 50 is the same as 50% of 18, which is just 9.

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Percentage Calculator

Three calculations, instantly, with the method shown so you can check the answer rather than just take it.

Percentage Calculator Canada

Solve percentage problems, percent changes, and Canadian GST/HST taxes instantly.

Mode 1: Percentage of a Number

Percentage (%)

Of Amount ($)

Result:37.50

Mode 2: Percentage Portion

Number X

Is what % of Y

Result:25.00%

Mode 3: Percentage Increase / Decrease

From Value (X)

To Value (Y)

Change (Increase):+25%

Mode 4: Canadian Sales Tax (GST/HST)

Pre-Tax Amount ($)

Province

Tax: $13Total: $113

The Three Core Calculations

Almost every percentage problem is one of these three.

What is X% of Y?

Y × (X ÷ 100)

15% of 80 = 80 × 0.15 = 12

Use for: tips, sales tax, discounts, commission, interest on balances.

X is what % of Y?

(X ÷ Y) × 100

12 is what % of 80 = (12 ÷ 80) × 100 = 15%

Use for: test scores, share of income, progress completion rates.

% Change from X to Y

((Y less X) ÷ X) × 100

80 to 92 = ((92 less 80) ÷ 80) × 100 = +15%

Use for: price changes, investment returns, year over year comparisons.

The critical detail is the denominator: you divide by the original value, not the new one. Getting that backwards is the most common percentage error there is.

Doing Percentages in Your Head

Start with 10% by moving the decimal one place left. For example, 10% of $84 is $8.40. From there, build:

5%: Half of 10% → $4.20

20%: Double 10% → $16.80

15%: 10% + 5% → $12.60

1%: Move decimal 2 places → $0.84

25%: Quarter (divide by 4) → $21.00

Reversal Trick: 18% of 50 = 50% of 18 = 9

Percentage Increase and Decrease Aren't Symmetric

A 50% decrease is not undone by a 50% increase. If $100 falls 50%, it becomes $50. A 50% rise on $50 gives $75, not $100. To recover from $50 back to $100, you need a 100% gain because the base changes.

Loss	Gain Required to Break Even
10%	11.1%
20%	25%
33%	50%
50%	100%
75%	300%
90%	900%

Percentage Points vs Percent

The Distinction in Canadian Finance:

If a mortgage rate moves from 4% to 5%, that is an increase of 1 percentage point, but a 25% relative increase in the interest rate. Both are correct, but they are not interchangeable.

Bank of Canada interest rate announcements are quoted in basis points (1 basis point = 0.01 percentage points, so a 25 basis point cut equals 0.25 percentage points).

Stacked Discounts & Reverse Percentages

Stacked Discounts Don't Add Up

"20% off, then an extra 10% off" is 28% off, not 30%. The second discount applies to the already reduced price ($100 less 20% = $80; $80 less 10% = $72).

Combined = 1 less (1 less a) × (1 less b) = 28%

Reverse Percentages (Removing Tax)

To find pre tax price from a tax inclusive total, divide by (1 + rate). For Ontario 13% HST on a $113 total: $113 ÷ 1.13 = $100 (never subtract 13%, which incorrectly gives $98.31).

Original Price = Final Price ÷ (1 + Tax Rate)

Sales Tax Percentages Across Canada

Province / Territory	Combined Rate	Tax on $50
Alberta, NWT, Nunavut, Yukon	5%	$2.50
Saskatchewan	11%	$5.50
British Columbia, Manitoba	12%	$6.00
Ontario	13%	$6.50
Nova Scotia	14%	$7.00
Quebec	14.975%	$7.49
New Brunswick, Newfoundland and Labrador, PEI	15%	$7.50

Tipping, and the Tax Line Shortcut

In Canada, standard restaurant tipping is 15 to 20% on the pre tax bill (15% adequate, 18% standard norm, 20%+ excellent).

Jurisdiction	Tax Rate	Does Tax Line Shortcut Work for 15% Tip?
NB, NL, PEI	15%	Perfect: tax line equals exactly a 15% tip
Quebec	14.975%	Effectively exact shortcut
Nova Scotia	14%	Close, slightly under 15%
Ontario	13%	A little under standard
BC, Manitoba, Saskatchewan	11% to 12%	Under standard
Alberta, Territories	5%	Does not work: doubling 5% GST is only 10%

Markup vs Margin

An item costing $60 that sells for $100 generates $40 profit:

Markup = 66.7%(Profit ÷ Cost) × 100 = (40 ÷ 60) × 100. Measured against what you paid.

Margin = 40.0%(Profit ÷ Selling Price) × 100 = (40 ÷ 100) × 100. Measured against what you charged.

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Frequently Asked Questions

Method and Sources

Sources: Standard percentage arithmetic with working shown for full transparency. Canadian sales tax rates maintained with Canada Revenue Agency and Revenu Québec. Tipping norms reflect customary Canadian consumer practice.

Disclaimer: CalcVault provides financial calculations for informational purposes. Tipping and commercial pricing decisions reflect individual discretion.