I like floorplanner.com
You get one free design ....but when I want to try something else I do a second..third..fourth etc floor I have a house with 9 floors!!
You can pay to upgrade , but the free version works for me.
Shows 3D as well.
Can place furniture, flooring, Windows etc

the graph paper is a great place to start but doesn't allow for differing thicknesses of internal and external walls and even minor variations in wall covering like tiles on bathroom walls..the best measurements are taken along the whole wall ignoring window, doors, built ins and kitchen cupboards..focus on the main walls first to find the inside size of the rooms and then add the extras details last..if you plan to do a renovation you'll need to later have professional plans drawn up for a development application, site plans, Basix etc so a rough plan of the inside spaces with a 10cm wall will give a reasonable approximation that will have to be fine tuned by an accurate site inspection by whoever does final plans ..my rough draught of your plan shows a basic outline but highlights some questions and discrepancies with measurements that i can't see properly but what's the narrow space between garage and bed 2, what's the small space next to the bathroom and what would you like to add?

As there's no WC marked in the Bathroom I think that space could be the WC?

Roomsketcher is great can add furniture as well

Thanks everyone for your suggestions.
Thanks oklouise that looks fantastic. The narrow space is a breezeway and has a security door at the front and a main wooden door just where u hv it. There is a sliding glass door between the garage and the breezeway and there is a laundry in the space b4 the bathroom

I’d like to try and make it 2 bedroom 2 bathroom. I was thinking about putting a cavity door at bedroom 2 and turning the laundry into a 2nd bathroom (toilet and shower) and putting a washing machine in the kitchen. I also need to redesign the kitchen. So many ideas however I’m on a budget 😊

you should be able to make two small bathrooms without changing the bedroom walls but you need to make the two spaces at least the sizes shown to make enough walking space for both bathrooms.. i've included standard sized vanities and showers but allowed 80cm x 80cm for toilets as, although you can buy much smaller toilets, the extra space is needed for knees and elbows... especially when the toilets are squeezed into a corner

adding a washing machine to the kitchen might be possible but possibly not legal and would be expensive to rearrange an existing kitchen unless you're adding all new cabinets so consider adding a European laundry into the garage accessed from the entry or at the end of the patio accessed from the kitchen..

I’d try and squeeze in a European laundry