Auto Sum?

Currently the only calculations Gravity Forms performs are related to the Pricing Fields for creating order forms. There isn't currently a built in option or specialized field types for performing general calculations. If you needed to implement something like this you would have to do so as a customization using custom jQuery. Calculations is a feature we plan on adding in the future.

The problem is the pricing fields display currency. It might be possible to do it as a hack using the Pricing Fields and finding a way around the currency issue but it would still be a hack and probably not ideal.

There may be other ways to implement it as a customization but I just can't think of any that are easily explainable off the top of my head.

If you aren't comfortable implementing it as a customization you could either hire a developer to implement it for you as a customization or wait for it to be added as a built in feature.

I can't give you a timeframe. We don't provide specific timeframe for features because we don't want to set unreasonable expectations. We develop features based on user demand, market conditions and development time. We already have a list of features we plan on introducing in the next major feature release, so it won't be in that release. So it would not be until later this year.

You would have to use the gform_currencies hook to modify an existing currency or create a new one that doesn't have a currency symbol. Documentation for the gform_currencies hook can be found here:

http://www.gravityhelp.com/documentation/page/Gform_currencies

However one thing to keep in mind is the calculations would still be treated as currency so this could pose some display issues as currency is typically displayed different than standard numeric values.