How can I get input radio elements to horizontally align in react [material-ui]?

To render the radio buttons in a row:

<RadioButtonGroup style={{ display: 'flex' }}>

To reset sizing according to content:

<RadioButton style={{ width: 'auto' }} />

Simply add the prop row={true} on the RadioGroup control.

 <RadioGroup
      aria-label="Location"
      name="location"
      className={classes.group}
      value={location}
      onChange={handleChange}
      row={true}
      >
         <FormControlLabel value="company" control={<Radio />} label="Company" />
         <FormControlLabel value="home" control={<Radio />} label="Home" />
         <FormControlLabel value="other" control={<Radio />} label="Other" />
 </RadioGroup>

Simply use the row property:

<RadioGroup row><Radio /><Radio /></RadioGroup>

RadioGroup inherits from FormGroup so the properties of the FormGroup component are also available.

Another example, with labels:

<RadioGroup aria-label="anonymous" name="anonymous" value={false} row>
  <FormControlLabel value="true" control={<Radio />} label="Yes" />
  <FormControlLabel value="false" control={<Radio />} label="No" />
</RadioGroup>

For those who are still struggling, use this style:

const styles = theme => ({
    group: {
        width: 'auto',
        height: 'auto',
        display: 'flex',
        flexWrap: 'nowrap',
        flexDirection: 'row',
    }
});

class MyComponent extends React.Component {

    render() {
        const { classes } = this.props;

        <RadioGroup className={classes.group} ...>
    }

};

export default withStyles(styles)(MyComponent);