Position Size Calculator in Excel / Google Sheets — Free Formula

Some traders prefer a spreadsheet over an online calculator. It logs every trade, calculates position size automatically, and can include custom fields like risk/reward ratio, commission, and notes. Here is the exact formula and a ready-to-use template layout.

The Core Formula

In Excel or Google Sheets:

=A2*B2/(C2-D2)

Cell	Column	Example Value
A2	Account Size	50000
B2	Risk % (as decimal)	0.01
C2	Entry Price	150.00
D2	Stop Loss Price	142.00
E2 (formula)	Position Size (shares)	=A2*B2/(C2-D2) = 62.5

Round down to 62 shares. Never round up - rounding up increases your risk beyond the target percentage.

Complete Trading Spreadsheet Layout

Column	Header	Formula/Input	Purpose
A	Date	Manual input	When you planned the trade
B	Symbol	Manual input	Stock/pair ticker
C	Account Size	Manual input	Current account balance
D	Risk %	Manual input (0.01 = 1%)	Your risk percentage
E	Dollar Risk	=C*D	Maximum $ you can lose
F	Entry Price	Manual input	Planned entry price
G	Stop Loss	Manual input	Stop loss price
H	Risk Per Share	=F-G	Price distance to stop
I	Position Size	=E/H	Number of shares to buy
J	Position Value	=I*F	Total dollar value of position
K	% of Account	=J/C	Position as % of account
L	Target Price	Manual input	Profit target
M	Reward/Risk	=(L-F)/(F-G)	Risk-to-reward ratio
N	Notes	Manual input	Trade thesis, setup type

Forex Lot Size Columns

Add these columns if you trade forex:

Column	Header	Formula	Purpose
O	Units	=E/H	Raw position in units
P	Standard Lots	=O/100000	Standard lots (100K units)
Q	Mini Lots	=O/10000	Mini lots (10K units)
R	Micro Lots	=O/1000	Micro lots (1K units)

Useful Extra Formulas

Purpose	Formula	Example
Max loss in dollars	=I*(F-G)	62 shares x $8 gap = $496
Profit at target	=I*(L-F)	62 shares x $15 gain = $930
Risk/reward ratio	=(L-F)/(F-G)	$15/$8 = 1.88:1
Win rate needed to break even	=1/(1+M)	1/(1+1.88) = 34.7%
Round down shares	=FLOOR(E/H,1)	Forces whole number, rounds down
Commission impact	=Comm*2 (round trip)	$0.005 x 62 shares x 2 = $0.62

Step-by-Step Setup

1. Open Google Sheets (free) or Excel
2. Create headers in Row 1 matching the table above
3. Enter your account size, risk %, entry price, and stop loss in Row 2
4. Enter the position size formula in cell I2: =FLOOR(C2*D2/(F2-G2),1)
5. Copy the formulas for all calculated columns
6. Each new trade goes in a new row. Update Account Size to your current balance

Spreadsheet vs Online Calculator

	Spreadsheet	Online Calculator
Speed	Moderate (open sheet, enter values)	Fast (bookmark, enter, done)
Trade logging	Built in (every row is a trade)	No logging
Custom columns	Unlimited	Fixed inputs
Mobile access	Google Sheets app or browser	Any browser
Formula errors	Possible if setup wrong	Pre-built, tested
Cost	Free (Google Sheets)	Free
Best for	Journaling + sizing	Quick pre-trade sizing

Both Options - Free

• Position Size Calculator - instant calculation, no spreadsheet needed
• The 1% Risk Rule - the foundation of position sizing
• How Many Shares to Buy - the complete formula guide