Percentage Formulas in Excel: Growth, Share, Discount, Margin and GST

Q: How do I calculate percentage increase in Excel?

=(New-Old)/Old , then format as %. 40,000 to 46,000 is 15%.

Q: How do I find the price before GST?

Divide by 1 plus the rate: =A2/(1+18%) .

Q: How do I show a negative change in red?

Use a custom format like 0.0%;[Red]-0.0% (Ctrl + 1 > Number > Custom).

By Ravindra Bagale, Excel & Data Analytics trainer LinkedIn Published: 6 October 2026 Last updated: 6 October 2026

Zoya's shop sold ₹40,000 in August and ₹46,000 in September. Her accountant asks, “What is the growth?” The difference is ₹6,000, and ₹6,000 out of the old ₹40,000 is 15%. Every percentage question is like this: a part divided by the right whole.

A percentage is a fraction shown with the % format. Excel stores 15% as 0.15. Write the division (part ÷ whole), then press Ctrl + Shift + % or use Home > % to show it as a percentage.

Download the practice file (percentage-formulas.xlsx)

Excel file, 6 KB. It has the sample data used below. All numbers in this workbook are fictional teaching data, not real company figures.

Quick answer

Old value in A2 (40000), new value in B2 (46000).
Growth: =(B2-A2)/A2.
Press Enter, then Ctrl + Shift + %.
The cell shows 15%.
For other questions pick the formula from the table below.

=(B2-A2)/A2

The formulas

Question	Example	Formula	Answer
% change (growth)	40,000 → 46,000	`=(B2-A2)/A2`	15%
% of total	Pune 18,000 of 60,000	`=B5/$B$11`	30%
Add 10%	Price 500 in B13	`=B13*(1+10%)`	550
Remove 15% (discount)	MRP 1,200 in B16	`=B16*(1-15%)`	1,020
What % is the discount?	MRP 1,200 in B16, sold at 1,020 in C17	`=(B16-C17)/B16`	15%
Margin (on price)	Cost 80 in B18, price 100 in C18	`=(C18-B18)/C18`	20%
Markup (on cost)	Cost 80 in B18, price 100 in C18	`=(C18-B18)/B18`	25%
Base price from GST-inclusive amount (18%)	1,180 incl. GST in B14	`=B14/(1+18%)`	1,000
GST inside that amount	1,180 incl. GST in B14	`=B14-B14/(1+18%)`	180

% of total: lock the total with $

City	Sales	Share =B5/$B$11
Pune	18,000	30%
Nashik	12,000	20%
Nagpur	9,000	15%
Solapur	6,000	10%
Kolhapur	9,000	15%
Sambhaji Nagar	6,000	10%
Total	60,000	100%

Cities are in rows 5 to 10 and the total is in B11. The $ in $B$11 keeps the total fixed when you copy the formula down. Without it, the next row would divide by B12, which is empty, and show #DIV/0!.

Margin is not markup

Both use the same profit (100 - 80 = 20). Margin divides by the selling price (20 ÷ 100 = 20%). Markup divides by the cost (20 ÷ 80 = 25%). Retail and finance reports usually mean margin; always say which one you show.

Percent vs percentage points

If on-time delivery goes from 80% to 88%, it rose by 8 percentage points (88 - 80) but by 10 percent ((88 - 80) ÷ 80). Write "pp" or "points" when you subtract two percentages.

Ravindra Bagale's Tip

Type percentages as 18% (with the sign) or as 0.18, never as 18 in a cell that you then divide by 100 in some formulas and not in others. Mixed styles are the number one cause of 100× errors I see.

Practice task

Open the Percent sheet. Check C2 shows 15%.
Change B2 to 50000. Growth becomes 25%.
Check the share column C5:C10 adds up to 100% in C11.
Check the reverse GST answer in D14 (1000).
Work out the markup if cost is 120 and price is 150. Expect 25%.

Learn it properly

Course lessons:

Frequently asked questions

How do I calculate percentage increase in Excel?

=(New-Old)/Old, then format as %. 40,000 to 46,000 is 15%.

Why does my percentage show 1500%?

The cell already had a % format and you multiplied by 100. Remove the *100.

How do I find the price before GST?

Divide by 1 plus the rate: =A2/(1+18%).

How do I show a negative change in red?

Use a custom format like 0.0%;[Red]-0.0% (Ctrl + 1 > Number > Custom).