ValueError: could not convert string to float: '<kivy.uix.textinput.TextInput object at 0x0000011D49678430>'

Question

I'm new at python and right now i try to make similar calculator with user input. I rewrote my code but its still dont work fine. Cant convert string property to a float. All time i just get "ValueError: could not convert string to float: '<kivy.uix.textinput.TextInput object at 0x0000011D49678430>'" Can someone help me with fix this issue and give me some advices? My code :

from kivy.app import App
from kivy.uix.gridlayout import GridLayout
from kivy.uix.label import Label
from kivy.uix.button import Button
from kivy.uix.textinput import TextInput
from kivy.properties import NumericProperty


class calculate(GridLayout):
    def __init__(self, **kwargs):
        super(calculate, self).__init__(**kwargs)
        self.cols = 2
        self.rows = 5

        self.label1 = Label(text='Width in mm : ')
        self.add_widget(self.label1)

        self.user_data1 = TextInput(multiline=False)
        self.add_widget(self.user_data1)

        self.label2 = Label(text='Height in mm : ')
        self.add_widget(self.label2)

        self.user_data2 = TextInput(multiline=False)
        self.add_widget(self.user_data2)

        self.label3 = Label(text='Mass in gr : ')
        self.add_widget(self.label3)

        self.user_data3 = TextInput(multiline=False)
        self.add_widget(self.user_data3)

        self.label4 = Label(text='Mass in kg : ')
        self.add_widget(self.label4)

        self.user_data4 = TextInput(multiline=False)
        self.add_widget(self.user_data4)

        self.button = Button(text='Calculate')
        self.button.bind(on_press=self.on_user_press)
        self.add_widget(self.button)

        self.calculate = Label(text='')
        self.add_widget(self.calculate)

    def on_user_press(self, event):
        s_kg = str(self.user_data4)
        s_width = str(self.user_data1)
        s_height = str(self.user_data2)
        s_gr = str(self.user_data3)

        f_kg = float(s_kg)
        f_width = float(s_width)
        f_height = float(s_height)
        f_gr = float(s_gr)

        value = f_kg / (f_width / 1000) / (f_height / 1000) / (f_gr / 1000)
        string_value = str(value)
        self.calculate.text = string_value




class Calculator(App):
    def build(self):
        return calculate()


if __name__ == "__main__":
    Calculator().run()