It’s SABR time: What is wRC+?

Today, we’ll explore the single-most all-important advanced hitting statistic that exists, and that’s Weighted Runs Created Plus, or wRC+ for short. Here’s the glossary in Fangraphs’ words, but I’ll try to synthesize this quicker in an attempt to make this more accessible.

wRC+ was created in an attempt to boil down each hitter’s effectiveness down to a single number. Batting average is a measure of how often a player gets a hit, on-base percentage states how often a player gets on-base, and slugging percentage shows a rough quantification of a batter’s power. But which of these should you put faith in most when each batter has a uniquely different contact, power, and speed profile?

Though OPS (on base plus slugging) attempts to do this, it is not accurate because it assumes one point of slugging is equivalent to one point of OBP. In actuality, the ratio between the two is OBP is 1.8x as valuable as SLG.

Weighted on-base average, or wOBA, corrects for this mathematical injustice with the following calculation for each hitter by appropriately weighting each event for each batter with the following calculation. You can judge wOBA on the same scale as you would OBP.

But wOBA does not account for the differences in park factor (since each stadium is of different dimensions), nor does it account for league factor, also poignant since the offensive capabilities of a pitcher and a designated hitter are remarkably disparate.

wRC+ takes wOBA a step further by first converting wOBA to wRC.

wRC = (((wOBA-League wOBA)/wOBA Scale)+(League R/PA))*PA

Then the wRC is park-adjusted and league-adjusted, becoming wRC+ on a scale of 100, where higher is better than average and lower is worse than average.

wRC+ = (((wRAA/PA + League R/PA) + (League R/PA – Park Factor* League R/PA))/ (AL or NL wRC/PA excluding pitchers))*100

The league’s wRAA (weighted runs above average) per plate appearance, R/PA (runs per plate appearance), and wRC/PA all depend on the run-scoring environment of that year, putting it on a scale of 100.

The result is a singular number that can be used to compare any player to any other player, regardless of when a player played.

Take it from Fangraphs themselves.

If you want a rate statistic for hitters that weights each offensive action and controls for league and park effects, wRC+ is for you. While wOBA is a huge step forward from stats like batting average and slugging percentage, it doesn’t credit hitters who play in difficult parks or deduct points for hitters who play in smaller ones. wRC+ brings all the virtues of wOBA plus two added benefits; park and league adjustments. A .400 wOBA at Coors is much less impressive than one at Petco, for example. Additionally, wOBA tracks with overall league offense, so you can’t use it to compare players of different eras very effectively. A .400 wOBA in 2000 is much less impressive than one in 2014, but a 140 wRC+ in 2000 means essentially the same thing in 2014.

So how to use wRC+? Here’s an example.

Mike Trout is sporting a godly 208 wRC+ this year. Translation? He’s hitting 108% better than a league average player. He owns a career 170 wRC+ (throughout his career, he is a 70% better than league average hitter).

It works the other way as well. Ben Revere has a 45 wRC+; that means he is hitting 55% worse than league average.

When you hear any use of wRC+ in an article, don’t be so scared! It’s actually pretty easy to understand, and that’s why it was created in the first place. It puts each hitter on a level playing field that counting stats, batting average, slugging, and OPS cannot do, and that’s why it is the most useful advanced hitting metric available. It can most easily be accessed on Fangraphs.com, the fifth to last column on a player page.