Priming calculators giving me drastically different amounts

[KepowOb]

So I use Beersmith to figure out everything for my recipes.

For a 5.25 gallon batch, priming with table sugar, and to get a carbonation level of 2.5 it said to use 3.76oz of table sugar, which seemed a bit low to me (my beer is at 74F).

I took the same numbers and plugged them into the Brewers Friend priming calculator and it gives me 4.8oz.

That seems like a rather drastic difference, even if they use different methods to calculate things. I've gone over both calculators and I'm pretty sure I've got them both set up correctly, but I feel like I must be missing something in beersmith. Anyone got any ideas?

 

[LoloMT7]

Looks like the Brewers Friend one is more accurate to me. I like this one myself and it shows 4.65 oz Sucrose (table sugar) for 5.5 gallons @ 74 carbed to 2.5. Maybe a setting isn't right in beersmith ? I'm not sure on that. http://www.northernbrewer.com/priming-sugar-calculator/

 

[Spartangreen]

The northernbrewer one always works for me.

 

[flars]

I only use The Beer Recipator to establish consistency for carbonation. When the numbers I input seem to end up with an under or over carbed batch, I adjust for the next one. Carbonation calculations are an important part of my notes for when I have the first and last bottle from a batch.
http://hbd.org/cgi-bin/recipator/recipator/carbonation.html?14635422#tag

When I do run into an over carbonated or under carbonated batch I also look at my brewing notes. May have just screwed up somewhere.