Length Converter

#include <iostream>

using namespace std;

void NauticalMile(double nm);
void Mile(double mile);
void Yard(double yard);
void Meter(double meter);
void Foot(double ft);
void Inch(double in);
void Centimeter(double cm);
void Millimeter(double mm);
void Kilometer(double km);

int main()
{

    int sel = 0;

    cout << "                        Welcome to the Length Converter" << endl;
    cout << "                               Version: 0.5.0" << endl;
    cout << "                              Made by: Marc G." << endl << endl;

    while (sel != -1) {

        cout << "[1] Nautical Mile\n[2] Mile\n[3] Yard\n[4] Meter\n[5] Foot\n[6] Inch\n[7] Centimeter\n[8] Millimeter\n[9] Kilometer" << endl;
        cout << "Please pick one (Type -1 to Exit!): ";
        cin >> sel;
        cout << endl;

        if (cin.fail())
        {
            cout << "----------------------------------" << endl;
            cout << "Error: String Entry Detected - Terminating Program!" << endl;;
            cout << "----------------------------------" << endl << endl;
            system("PAUSE");
            return 0;
        }

        switch (sel)
        {
        case 1:
            double lnm;

            cout << "Choose how many Nautical Miles: ";
            cin >> lnm;
            cout << endl;

            NauticalMile(lnm);
            break;
        case 2:
            double lmile;

            cout << "Choose how many Miles: ";
            cin >> lmile;
            cout << endl;

            Mile(lmile);
            break;
        case 3:
            double lyard;

            cout << "Choose how many Yards: ";
            cin >> lyard;
            cout << endl;
            break;
        case 4:
            double lmeter;

            cout << "Choose how many Meters: ";
            cin >> lmeter;
            cout << endl;

            Meter(lmeter);
            break;
        case 5:
            double lft;

            cout << "Choose how many Feet: ";
            cin >> lft;
            cout << endl;

            Foot(lft);
            break;
        case 6:
            double lin;

            cout << "Choose how many Inches: ";
            cin >> lin;
            cout << endl;

            Inch(lin);
            break;
        case 7:
            double lcm;

            cout << "Choose how many Centimeters: ";
            cin >> lcm;
            cout << endl;

            Centimeter(lcm);
            break;
        case 8:
            double lmm;

            cout << "Choose how many Millimeters: ";
            cin >> lmm;
            cout << endl;

            Millimeter(lmm);
            break;
        case 9:
            double lkm;

            cout << "Choose how many Kilometers: ";
            cin >> lkm;
            cout << endl;

            Kilometer(lkm);
            break;
        case -1:
            return 0;
            break;
        default:
            cout << "----------------------------------" << endl;
            cout << "Please select one of the options on the list!" << endl;
            cout << "----------------------------------" << endl << endl;
        }
    }
    system("PAUSE");
    return 0;
}

void NauticalMile(double nm)
{
    double lmile, lyard, lmeter, lft, lin, lcm, lmm, lkm;

    lmile = nm * 1.15078;
    lyard = nm * 2025.37;
    lmeter = nm * 1852;
    lft = nm * 6076.12;
    lin = nm * 72913.4;
    lcm = nm * 185200;
    lmm = nm * 1.852e+6;
    lkm = nm * 1.852;

    cout << "----------------------------------" << endl;
    cout << "Miles: " << lmile << endl;
    cout << "Yards: " << lyard << endl;
    cout << "Meters: " << lmeter << endl;
    cout << "Feet: " << lft << endl;
    cout << "Inches: " << lin << endl;
    cout << "Centimeters: " << lcm << endl;
    cout << "Millimeters: " << lmm << endl;
    cout << "Kilometers: " << lkm << endl;
    cout << "----------------------------------" << endl << endl;
}

void Mile(double mile)
{
    double lnm, lyard, lmeter, lft, lin, lcm, lmm, lkm;

    lnm = mile * 0.868976;
    lyard = mile * 1760;
    lmeter = mile * 1609.34;
    lft = mile * 5280;
    lin = mile * 63360;
    lcm = mile * 160934;
    lmm = mile * 1.609e+6;
    lkm = mile * 1.60934;

    cout << "----------------------------------" << endl;
    cout << "Nautical Miles: " << lnm << endl;
    cout << "Yards: " << lyard << endl;
    cout << "Meters: " << lmeter << endl;
    cout << "Feet: " << lft << endl;
    cout << "Inches: " << lin << endl;
    cout << "Centimeters: " << lcm << endl;
    cout << "Millimeters: " << lmm << endl;
    cout << "Kilometers: " << lkm << endl;
    cout << "----------------------------------" << endl << endl;
}

void Yard(double yard)
{
    double lnm, lmile, lmeter, lft, lin, lcm, lmm, lkm;

    lnm = yard * 0.000493737;
    lmile = yard * 0.000568182;
    lmeter = yard * 0.9144;
    lft = yard * 3;
    lin = yard * 36;
    lcm = yard * 91.44;
    lmm = yard * 914.4;
    lkm = yard * 0.0009144;

    cout << "----------------------------------" << endl;
    cout << "Nautical Miles: " << lnm << endl;
    cout << "Miles: " << lmile << endl;
    cout << "Meters: " << lmeter << endl;
    cout << "Feet: " << lft << endl;
    cout << "Inches: " << lin << endl;
    cout << "Centimeters: " << lcm << endl;
    cout << "Millimeters: " << lmm << endl;
    cout << "Kilometers: " << lkm << endl;
    cout << "----------------------------------" << endl << endl;
}

void Meter(double meter)
{
    double lnm, lmile, lyard, lft, lin, lcm, lmm, lkm;

    lnm = meter * 0.000539957;
    lmile = meter * 0.000621371;
    lyard = meter * 1.09361;
    lft = meter * 3.28084;
    lin = meter * 39.3701;
    lcm = meter * 100;
    lmm = meter * 1000;
    lkm = meter * 0.001;

    cout << "----------------------------------" << endl;
    cout << "Nautical Miles: " << lnm << endl;
    cout << "Miles: " << lmile << endl;
    cout << "Yards: " << lyard << endl;
    cout << "Feet: " << lft << endl;
    cout << "Inches: " << lin << endl;
    cout << "Centimeters: " << lcm << endl;
    cout << "Millimeters: " << lmm << endl;
    cout << "Kilometers: " << lkm << endl;
    cout << "----------------------------------" << endl << endl;
}

void Foot(double ft)
{
    double lnm, lmile, lyard, lmeter, lin, lcm, lmm, lkm;

    lnm = ft * 0.000164579;
    lmile = ft * 0.000189394;
    lyard = ft * 0.333333;
    lmeter = ft * 0.3048;
    lin = ft * 12;
    lcm = ft * 30.48;
    lmm = ft * 304.8;
    lkm = ft * 0.0003048;

    cout << "----------------------------------" << endl;
    cout << "Nautical Miles: " << lnm << endl;
    cout << "Miles: " << lmile << endl;
    cout << "Yards: " << lyard << endl;
    cout << "Meters: " << lmeter << endl;
    cout << "Inches: " << lin << endl;
    cout << "Centimeters: " << lcm << endl;
    cout << "Millimeters: " << lmm << endl;
    cout << "Kilometers: " << lkm << endl;
    cout << "----------------------------------" << endl << endl;
}

void Inch(double in)
{
    double lnm, lmile, lyard, lmeter, lft, lcm, lmm, lkm;

    lnm = in * 1.3715e-5;
    lmile = in * 1.5783e-5;
    lyard = in * 0.0277778;
    lmeter = in * 0.0254;
    lft = in * 0.0833333;
    lcm = in * 2.54;
    lmm = in * 25.4;
    lkm = in * 2.54e-5;

    cout << "----------------------------------" << endl;
    cout << "Nautical Miles: " << lnm << endl;
    cout << "Miles: " << lmile << endl;
    cout << "Yards: " << lyard << endl;
    cout << "Meters: " << lmeter << endl;
    cout << "Feet: " << lft << endl;
    cout << "Centimeters: " << lcm << endl;
    cout << "Millimeters: " << lmm << endl;
    cout << "Kilometers: " << lkm << endl;
    cout << "----------------------------------" << endl << endl;
}

void Centimeter(double cm)
{
    double lnm, lmile, lyard, lmeter, lft, lin, lmm, lkm;

    lnm = cm * 5.3996e-6;
    lmile = cm * 6.2137e-6;
    lyard = cm * 0.0109361;
    lmeter = cm * 0.01;
    lft = cm * 0.0328084;
    lin = cm * 0.393701;
    lmm = cm * 10;
    lkm = cm * 1e-5;

    cout << "----------------------------------" << endl;
    cout << "Nautical Miles: " << lnm << endl;
    cout << "Miles: " << lmile << endl;
    cout << "Yards: " << lyard << endl;
    cout << "Meters: " << lmeter << endl;
    cout << "Feet: " << lft << endl;
    cout << "Inches: " << lin << endl;
    cout << "Millimeters: " << lmm << endl;
    cout << "Kilometers: " << lkm << endl;
    cout << "----------------------------------" << endl << endl;
}

void Millimeter(double mm)
{
    double lnm, lmile, lyard, lmeter, lft, lin, lcm, lkm;

    lnm = mm * 5.3996e-6;
    lmile = mm * 6.2137e-6;
    lyard = mm * 0.00109361;
    lmeter = mm * 0.001;
    lft = mm * 0.00328084;
    lin = mm * 0.0393701;
    lcm = mm * 0.1;
    lkm = mm * 1e-6;

    cout << "----------------------------------" << endl;
    cout << "Nautical Miles: " << lnm << endl;
    cout << "Miles: " << lmile << endl;
    cout << "Yards: " << lyard << endl;
    cout << "Meters: " << lmeter << endl;
    cout << "Feet: " << lft << endl;
    cout << "Inches: " << lin << endl;
    cout << "Centimeters: " << lcm << endl;
    cout << "Kilometers: " << lkm << endl;
    cout << "----------------------------------" << endl << endl;
}

void Kilometer(double km)
{
    double lnm, lmile, lyard, lmeter, lft, lin, lcm, lmm;

    lnm = km * 0.539957;
    lmile = km * 0.621371;
    lyard = km * 1093.61;
    lmeter = km * 1000;
    lft = km * 3280.84;
    lin = km * 39370.1;
    lcm = km * 100000;
    lmm = km * 1e+6;

    cout << "----------------------------------" << endl;
    cout << "Nautical Miles: " << lnm << endl;
    cout << "Miles: " << lmile << endl;
    cout << "Yards: " << lyard << endl;
    cout << "Meters: " << lmeter << endl;
    cout << "Feet: " << lft << endl;
    cout << "Inches: " << lin << endl;
    cout << "Centimeters: " << lcm << endl;
    cout << "Millimeters: " << lmm << endl;
    cout << "----------------------------------" << endl << endl;
}