Forex Position Size Calculator Help

This is the complete manual and help page for the Trader Rookie Forex Position Size Calculator - Browser Extension.


Rookie pointing at exclamation mark

Any information or advice included in this manual is general and does not constitute personal investment advice. Trader Rookie will not accept liability for any loss or damage including without limitation to any loss of profit which may arise directly or indirectly from the use of or reliance on such information and/or the use of the Trader Rookie Forex Position size calculator extension.

Using a position size calculator should by no means be considered insurance against losing your invested capital. Price gaps in markets, price slippage, and technical issues on your brokers trading platform are just a few examples where you potentially could lose more capital than your calculations indicated.

You should seek independent financial advice before acquiring the financial product or securities and financial products or instruments. Trading involves large financial risks and please remember that past performance results are not necessarily indicative of future results!

Table of Contents

  1. Quick start
  2. Why use a Position Size Calculator?
    1. What is trading?
    2. What is the difference between gambling and trading?
    3. Why calculate Position Sizes?
    4. What should I base my position size on?
  3. Calculator
    1. Change color theme
    2. Feedback survey
    3. Bug Report
    4. Reset input fields
    5. Repositioning the user-interface
    6. Hide the user-interface
    7. Price Dial
    8. Price Dial Buttons
    9. Position size
    10. Clipboard icons
    11. Settings page
    12. KO-FI
    13. Manual
    14. Adjust input with scroll wheel
    15. Leverage
    16. Toggle stoploss in PIPS or as price
    17. Toggle Position size in units or LOTS
    18. Long or short?
    19. Select tradepair
    20. Toggle Forex or Index & Commodity Trade Pairs
    21. Risk:Reward visual presentation
    22. Margin
    23. Risk
    24. Trade data
    25. Errors
  4. Navigation
    1. Mouse navigation
    2. Touch devices
    3. Keyboard shortcuts
  5. Setup Forex pairs
    1. Create a new forex pair
    2. Remove a forex pair from the calculator
    3. Add an index- or commodity pair to the calculator
    4. Remove an index- or commodity pair from the calculator
    5. Set leverage on forex pair(s)
    6. Setup Index and Commodity pair(s)
  6. Setup Index and Commodity pairs
    1. Individual trade pairs
    2. Select all
    3. Deselect all
    4. Construct new pair
    5. Adjust input for tradepairs
    6. Adjust leverage on tradepair(s)
    7. Set icon
  7. Settings
    1. Decimal separator
    2. Position LOT sizes
    3. Switch to compact layout
    4. Enable clipboard icons
    5. Enable mousescroll in input fields
    6. Reset extension
  8. Use the calculator with desktop broker software
    1. Open the calculator in a pop-up window
  9. Is the Browser Extension safe?
    1. Data Security
  10. Video Guides
    1. Introduction to the extension
  11. Questions & Answers
    1. How do I know when the calculations are updated?
    2. Can I use the calculator without an internet connection?
    3. How do I save the changes made on the settings page?
    4. Why do I need my broker's contract size specifications on Indices and Commodities?
    5. Can I find contract sizes and leverage directly in MetaTrader 4?
    6. Where can I read the privacy policy for the extension?
  12. Changelog
    1. Ver. 1.1.1
    2. Ver. 1.1.0
    3. Ver. 1.0.5
    4. Ver. 1.0.4
    5. Ver. 1.0.2
    6. Ver. 1.0.1

Quick start

Please refer to this page to get started using the extension: Quick start

Why use a Position Size Calculator?

Rookie unsure why he should use a position size calculator


map of the Forex Calculator


The different navigation types: Mouse Touch and keyboard

Setup Forex pairs

Settings drag and drop interface

Setup Index and Commodity pairs

Settings custom pair dialog box


The different settings types on the settings page

Use the calculator with desktop broker software

From forex calculator to Metatrader

Is the Browser Extension safe?


Video Guides

Questions & Answers

Trader Rookie Frequently Asked Questions graphics with orange cubes

How do I know when the calculations are updated '?

Checkmark from forex calculator when calculations are updated

The calculator has no "calculate button" per se. But when you make input changes or updates are made to settings, all calculations are updated instantly.

You will get a visual indication that calculations are updated in the left- hand output-area visualized by a checkmark.

Can I use the calculator without an internet connection?

Offline indicator showing that there is no internet connection when using the forex calculator

No, the calculator has no offline mode. All calculations rely on live exchange rates data.

If your internet connection is down for some reason, the calculator will indicate this with a large offline badge.

How do I save the changes made on the settings page?

You do not have to save anything.
All changes made on the settings page are synchronized instantly to any open calculators and stored for future use.

If you are signed into the browser all settings and input from the calculator will be synchronized automatically to all devices. Otherwise, the settings are stored locally on your computer.

Why do I need my broker's contract size specifications on Indices and Commodities?

Well, first off: You only need to pay attention to contract sizes if you calculate your position sizes in lots. All unit calculations are unaffected by the contract size.

Attention! pop-up dialog from Forex Calculator warning about inconsistencies between brokers about contract sizesBut if you trade with lot sizes, you need to get contract size data from your broker on the pairs you want to trade. Otherwise, you may unintentionally calculate position sizes with (potentially large) errors.
Index and Commodity pair contract sizes aren't standardized across brokers in the same way as with forex pairs.

You need to know how many units one contract consists of. This will typically be referred to, as something along the lines of "Contract size" or "Value of one contract".

A quick example:

Your broker offers "XAUUSD" or simply "Gold Cash" in contract sizes of  "100 troy ounces". Here the quote-currency for the trade-pair is USD.

Go to the "Setup Index and Commodity pairs dialog" and make sure "lot size" is set to "100" and "Currency" is set to "USD".

In this dialog, it is also recommended to set leverage on the trade-pair according to your broker's specifications.

Please refer to Setup Index and Commodity pairs dialog for further explanation on editing these values.

Can I find contract sizes and leverage directly in MetaTrader 4?


All contract sizes can be found for all trade pairs directly in Meta Trader.

  1. In the View menu select "Market Watch" or press Ctrl + M.Select Market Watch in Meta Trader 4

  2. In the market watch section right-click the tradepair you need to find the contract size for.Right-click the tradepair you need contract size for in Meta Trader 4

  3. In the right-click menu select "Specification".Click select specification in Meta Trader 4

  4. In the contract specification dialog you will now be able to see the contract size for this trade pair.The contract specification dialog contains info about contract size in Meta Trader 4

  5. To get leverage on the trade pair divide 100 by margin percentage.
    A margin percentage of 3.33% is equivialent to 30x margin and a margin percentage of 5% is equivialent to 20x margin.

Where can I read the privacy policy for the extension?

The privacy policy can be found here.

This will describe in detail the use of cookies and user data collected.


3 gear sprockets in different sizes

Ver. 1.1.2

April 22nd, 2021

  • - New forex data provider - The old data API endpoint suddenly stopped working.

Ver. 1.1.1

November 2nd, 2020

  • - Fixed a crucial font-error as a work-around for a bug in Chromium browsers.

Ver. 1.1.0

October 22nd, 2020

  • The extension visuals got a full makeover - I hope you like the new design!

  • Fixed a compatibility-issue with saxotraderGo (only relevant if SaxoBank is your broker) - you can now copy the price-data from the calculator seamlessly to Saxotrader.

  • Various "code optimization" behind the scenes - code is running smoother and faster using fewer resources.

  • Clipboard icons are now visible by default. They can still be turned off on the settings page.

Ver. 1.0.5

September 23rd, 2020

  • You can now just press enter to confirm input in input fields (you previously had to tab forward to the next field).

  • Default layout is now "compact" when installing the extension. You can still select the standard layout under settings.

  • All unused fields are now disabled when setting initial values - this is done to make the initial setup more intuitive and guided for new users.

  • Fixed an error, where the pop-up about contract size variances on index and commodity trade pairs, occurred more than once in some instances

Ver. 1.0.4

September 6th, 2020

  • A new compact layout is now available! Toggle between "standard" and "compact" layout on the settings page.

  • It is now possible to toggle between 3 different color themes! Switch theme on the color-brush in the upper right corner of the user-interface.

  • Fixed an error that prevented recalculations of position sizes when adjusting prices with the price-dial in some instances.

  • Fixed an error that allowed letter input in the risk input field.

Ver. 1.0.2

August 18th, 2020

  • Fixed a rare issue where stop-loss PnL and BAL values in the left side table sometimes didn't calculate correctly and showed "NaN".

  • Added some extra error messages on top of the left side table. These will better guide users to know what values are missing. Entry, stop-loss, etc.

  • Fixed an issue where the lower stop-loss output value wasn't removed if the calculator was reset from a different browser tab.

Ver. 1.0.1

August 7th, 2020

  • Initial release