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# std::chrono::duration_cast

From cppreference.com
< cpp‎ | chrono‎ | duration

template <class ToDuration, class Rep, class Period> constexpr ToDuration duration_cast(const duration<Rep,Period>& d); |  | (since C++11)

Converts a std::chrono::duration to a duration of different type `ToDuration`.

No implicit conversions are used. Multiplications and divisions are avoided where possible, if it is known at compile time that one or more parameters are 1. Computations are done in the widest type available and converted to the result type only when finished.

### [edit] Parameters

d | - | duration to convert

### [edit] Return value

`d` converted to a duration of type `ToDuration`.

### [edit] Notes

The function does not participate in the overload resolution unless `ToDuration` is an instance of std::chrono::duration.

Casting between floating-point durations or between integer durations where the source period is exactly divisible by the target period (e.g. hours to minutes) can be performed implicitly, no duration_cast is needed.

### [edit] Example

This example measures the execution time of a function

Run this code

    #include <iostream>
    #include <chrono>
    #include <thread>

    void f()
    {
        std::this_thread::sleep_for(std::chrono::seconds(1));
    }

    int main()
    {
        auto t1 = std::chrono::high_resolution_clock::now();
        f();
        auto t2 = std::chrono::high_resolution_clock::now();
        std::cout << "f() took "
                  << std::chrono::duration_cast<std::chrono::milliseconds>(t2 - t1).count()
                  << " milliseconds\n";
    }

Output:

    f() took 1000 milliseconds

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