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The Webster/Sainte-Laguë method is used in many electoral systems around the world, most notably in Germany, New Zealand, Norway and Sweden. But as with most proportional systems, although they produce fairer results they can be very difficult to figure out without some complex calculations.
This calculator can help you calculate the number of seats to award by proportional representation for an election using the Webster/Sainte-Laguë method.
This method uses the formula:
Co-efficient = Votes / ( (2 * Seats Earned) + 1 )
This makes it slightly more complicated than the D’Hondt formula (which you can find a calculator for here), but this calculator will help you award seats at the click of a button.
It also features support for an electoral threshold, which is a certain percentage (often 5%) of the vote that a party must win before it is awarded any proportional seats.
Click here to download the Webster/Sainte-Laguë calculator (in Microsoft Excel Macro-Enabled format)
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UPDATE 14th April 2019: Code fixes and improvements
UPDATE: 9th March 2021 – Added Creative Commons license to allow for adaptation of the work