public function toAll($decimals = null, $round = true)
    {
        if (!isset($this->value)) {
            throw new InvalidArgumentException('From value not set');
        }

        if (empty($this->base_unit)) {
            throw new InvalidArgumentException('No from unit set');
        }

        $units = array();

        foreach ($this->units as $key => $data) {
            if ($data['base'] == $this->base_unit) {
                array_push($units, $key);
            }
        }

        return $this->toMany($units, $decimals, $round);
    }