style.css

body {
    background-color: #F0F2F5;
    display: flex;
    flex-direction: column;
    padding-top: 5%;
    padding-bottom: 5%;
}

.calc {
    display: flex;
    flex-direction: column;
    margin: auto;
    margin-top: 30px;
    width: 50%;
    padding-bottom: 20px;
    background-color: #fff;
    border: 1px solid #D9DBDE;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.3);
    border-radius: 10px;
}

.objects {
    display: flex;
    margin: 25px;
    justify-content: space-evenly;
}

.objects > h3 {
    font-size: 25px;
    font-weight: 600;
    font-family: 'Source Sans Pro', sans-serif;
    margin-top: 0px;
    width: 50%;
    text-align: center;
}

input {
    height: 50px;
    width: 170px;
    padding-left: 10px;
    padding-right: 10px;
    box-shadow: 0 5px 15px rgba(73, 72, 72, 0.3);
    border-radius: 10px;
    outline: none;
    border: 1px solid rgba(0, 0, 0, 0.3);
    text-align: center;
    margin-left: 10px;
}

.result {
    padding: 10px;
    display: flex;
    justify-content: center;
}

h4 {
    margin: 0 10px;
    font-size: 20px;
    font-family: 'Mukta', sans-serif;
    font-weight: 600;
}

h1 {
    margin: auto;
    font-family: 'Mukta', sans-serif;
    font-weight: 600;
    color: #a8a6a6;
    text-align: center;
}

span {
    word-wrap: break-word;
    max-width: 70%;
    padding-top: 7px;
}

.calculate-div {
    text-align: center;
    padding: 20px 0;
}

.calculate-btn {
    
    height: 35px;
    width: 100px;
    border-radius: 10px;

}

.calculate-btn:hover {
    cursor: pointer;
}

@media (min-width: 900px) and (max-width: 1100px) {
    .calc {
        width: 65%;
    }
}

@media (max-width: 900px) {
    .calc {
        width: 80%;
    }
    .objects {
        flex-direction: column;
        align-items: center;
    }
    h3 {
        margin-bottom: 20px;
    }
    input {
        width: 150px;
        margin-left: 0;
    }
    .result {
        flex-direction: column;
        align-items: center;
    }
}