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/foil-print-velvet-dupatta-in-cream-mte1489-fh233090629Foil Print Velvet Dupatta in Creamhttps://medias.utsavfashion.com/media/catalog/product/cache/1/small_image/295x/040ec09b1e35df139433887a97daa66f/f/o/foil-print-velvet-dupatta-in-cream-v1-mte1489.jpg33.642USDInStock/men/men/wedding/men/velvet/men/white/men/dupattas/men/foil print/men/traditionalFoil Print Velvet Dupatta in Cream <ul><li> Velvet Dupatta in Cream</li><li> This attire is Enhanced with Fancy Tassels and All Over Foil Print</li><li> Its Length and Width are 96 and 18 inches respectively</li><li> Do note: Top, Bottom and Footwear shown in the image is for presentation purposes only. Half to one inch may vary in measurement. (Slight variation in actual color vs. image is possible)</li></ul>USDadd-to-carttype_new:Dupattascolorfam:Whitefabric:VelvetWhiteVelvetDupattas11%-20%MenReady to Ship, Within 2 days, Within 7 days, Within 10 days, Within 15 days, More than 15 DaysReadymadeWeddingMenswearFoil Print, Traditional