Sadaqah صدقة has no defined limit, unless you would spend and leave your family in need.
Sadaqah is recommended in the Qur'an and sunnah by verses such as:
And spend in the way of Allah and do not throw [yourselves] with your [own] hands into destruction [by refraining]. And do good; indeed, Allah loves the doers of good.
O you who have believed, spend from that which We have provided for you before there comes a Day in which there is no exchange and no friendship and no intercession. And the disbelievers - they are the wrongdoers. (2:254)
The example of those who spend their wealth in the way of Allah is like a seed [of grain] which grows seven spikes; in each spike is a hundred grains. And Allah multiplies [His reward] for whom He wills. And Allah is all-Encompassing and Knowing. (2:261)
O you who have believed, spend from the good things which you have earned and from that which We have produced for you from the earth. And do not aim toward the defective therefrom, spending [from that] while you would not take it [yourself] except with closed eyes. And know that Allah is Free of need and Praiseworthy. (2:267)
Take, [O, Muhammad], from their wealth a charity by which you purify them and cause them increase, and invoke [ Allah 's blessings] upon them. Indeed, your invocations are reassurance for them. And Allah is Hearing and Knowing. (9:103)
[O Muhammad], tell My servants who have believed to establish prayer and spend from what We have provided them, secretly and publicly, before a Day comes in which there will be no exchange, nor any friendships. (14:31)
and ahadith such as:
... 6) a person who practices charity so secretly that his left hand does not know what his right hand has given (i.e. nobody knows how much he has given in charity) ...
(In the hadith of the 7 who will be shaded by Allah under his shade, see for example in Sahih al-Bukhari)
Allah's Messenger (ﷺ) said, "If somebody gives in charity something equal to a date from his honestly earned money ----for nothing ascends to Allah except good---- then Allah will take it in His Right (Hand) and bring it up for its owner as anyone of you brings up a baby horse, till it becomes like a mountain." Abu Huraira said: The Prophet. said, "Nothing ascends to Allah except good." (See for example in Sahih al-Bukhari)
Note that being in charge for your family is a due and sadaqah is a recommended act of worship a duty or an ordered act stands always higher than an optional act and therefore if you spent too much and left your family hungry or in need your sadaqah even becomes a sinful act.
Nevertheless scholars said that one might even be allowed to spent any of his money or wealth which goes beyond what one needs for himself and his family:
The scholars of the four madhhabs are agreed that it is mustahabb for charity to be composed of whatever is surplus to one’s needs and the needs of those for whom one is responsible. If a person gives in charity that which affects his needs or the needs of those for whom he is responsible, that is a sin, because his spending on them is obligatory and it is not permissible to give precedence to a naafil (supererogatory) action over an obligatory one.
But with regard to whatever is surplus to the needs of those on whom a person is obliged to spend, the majority of scholars say that holding on to whatever wealth he needs is preferable to giving it all away in charity, unless he has an income or is sure that he will be able to put his trust in Allaah and be patient and steadfast in bearing poverty and will be able to refrain from begging. Some scholars regarded it as mustahabb to give all his wealth in that case.
The Shaafa’is regard this as being the most correct view, and it is the apparent meaning of al-Muwaffaq’s words in al-Mughni.
What may be understood from the Maaliki and Hanafi madhhabs is that they do not regard that as mustahabb, because after mentioning the above conditions concerning the permissibility of giving all one's wealth in charity, they say, “There is noting wrong with that,” as if the matter is permissible in their view. But some Maalikis add to that a comment which may be understood as meaning that they regard it as mustahabb, as they say, “The way of encouraging giving all one's wealth in charity is that the donor should feel good about it after giving all his wealth and should not feel regret about being without wealth or hope to gain a similar amount of wealth in the future. He should not have any need of it in the future for himself or for those on whom he is obliged or encouraged to spend. Otherwise it is not recommended for him (to give all his wealth in charity), rather it is haraam for him to do so if those on whom he is obliged to spend are in certain need, or it is makrooh for him to do so if he is certain that those on whom it is recommended for him to spend are in need, because it is better to give in charity that which is surplus to his needs and the needs of those on whom he is obliged to spend.”
(al-Mawsoo’ah al-Fiqhiyyah, 26/339) (Source islamqa #22881)
You may also find this fatwa on islamqa #72962 helpful in which it is asked whether an employee needs to give a certain amount of hius salary for charity (sadaqah).