the most robustest and fastest unit conversion library or your money back

fastconv.ts

type Quantity = symbol;

const Length: unique symbol = Symbol("Length quantity");

interface Unit<Q extends Quantity> {
    quantity: Q;
    factor: number;
}

export const Millimeter: Unit<typeof Length> = {
    quantity: Length,
    factor: 1,
};

export const Meter: Unit<typeof Length> = {
    quantity: Length,
    factor: 1000,
};

export const Inch: Unit<typeof Length> = {
    quantity: Length,
    factor: 25.4,
};

export const Foot: Unit<typeof Length> = {
    quantity: Length,
    factor: Inch.factor * 12,
};

const Volume: unique symbol = Symbol("Volume quantity");

export const Milliliter: Unit<typeof Volume> = {
    quantity: Volume,
    factor: 1,
};

export const Deciliter: Unit<typeof Volume> = {
    quantity: Volume,
    factor: 100,
};

export const Liter: Unit<typeof Volume> = {
    quantity: Volume,
    factor: 1000,
};

export const InchCubed: Unit<typeof Volume> = {
    quantity: Volume,
    factor: 16.387,
};

const Time: unique symbol = Symbol("Time quantity");

export const Second: Unit<typeof Time> = {
    quantity: Time,
    factor: 1000,
};

export const Minute: Unit<typeof Time> = {
    quantity: Time,
    factor: Second.factor * 60,
};

export const Hour: Unit<typeof Time> = {
    quantity: Time,
    factor: Minute.factor * 60,
};

export function convert<Q extends Quantity>(value: number, from: Unit<Q>, to: Unit<Q>): number {
    const ratio = from.factor / to.factor;
    return value * ratio;
}