You can always submit your measurement after placing the order. For now, just select Customize with Made to Measure, click Add to Shopping Bag and complete order. Later on go to Account section, visit My Orders page and submit your latest measurement.
If your bare chest size measurement is 40 inches, you should select size 40 only from the product page. The "Top Chest" attribute in the size chart refers to the garment's chest size. It is inclusive of the required 3 to 4 inches loosening, to ensure the right fit.
If your bare chest measurement falls between 2 sizes i.e 37 inches, you should select size 38.
https://www.utsavfashion.com/product/embroidered-art-silk-kurta-churidar-in-blue-mse2791530Embroidered Art Silk Kurta Churidar in Bluehttps://medias.utsavfashion.com/media/catalog/product/cache/1/small_image/295x/040ec09b1e35df139433887a97daa66f/m/s/mse279.jpg80.7595USDInStock/men/men/plus/men/party/men/art silk/men/blue/men/kurta pyjama/men/resham/men/traditionalEmbroidered Art Silk Kurta Churidar in Blue <ul><li> Art Silk Kurta in Blue</li><li> Designed with resham work on collar with placket</li><li> Available with white poly silk churidar</li><li> Do Note: Dupatta and mojari shown in the image is for photography purpose. Half to one inch may differ in measurement. (Slight color variation is possible.)</li></ul>USDtype_new:Kurta Pyjamacolorfam:Bluefabric:Art SilkBlueArt SilkKurta Pyjama11%-20%MenWithin 15 days, More than 15 DaysReadymadePartyMenswearResham, Traditional36, 38, 40, 4244, 46, 48, 50, 52, 54, 56, 58, 60