This will be helpful.

reading is your flow meter value in L/Hour

float reading;//value of the flow meter
long startTime;

void setup() {
  Serial.begin(9600);
  startTime=millis();

}

void loop() {
//read your flow meter to reading variable.
 Serial.println(reading*float((millis()-startTime))/3600000.0);

}

This will be helpful.

reading is your flow meter value in L/Hour

float reading;//value of the flow meter
long startTime;
float total=0;

void setup() {
  Serial.begin(9600);
  startTime=millis();

}

void loop() {
//read your flow meter to reading variable.
 total+=reading*float((millis()-startTime))/3600000.0;
 Serial.println(total);

}

This will be helpful.

reading is your flow meter value in L/Hour

float reading;//value of the flow meter
long startTime;

void setup() {
  Serial.begin(9600);
  startTime=millis();

}

void loop() {
 Serial.println(reading*float((millis()-startTime))/3600000.0);

}

This will be helpful.

reading is your flow meter value in L/Hour

float reading;//value of the flow meter
long startTime;

void setup() {
  Serial.begin(9600);
  startTime=millis();

}

void loop() {
//read your flow meter to reading variable.
 Serial.println(reading*float((millis()-startTime))/3600000.0);

}