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/chikankari-art-silk-sherwani-in-off-white-mte1541-fh233136725Chikankari Art Silk Sherwani in Off Whitehttps://medias.utsavfashion.com/media/catalog/product/cache/1/small_image/295x/040ec09b1e35df139433887a97daa66f/c/h/chikankari-art-silk-sherwani-in-off-white-v1-mte1541.jpg224.8281USDInStock/men/men/plus/men/wedding/men/art silk/men/white/men/sherwani/men/buttons/men/sequins/men/thread work/men/traditionalChikankari Art Silk Sherwani in Off White <ul><li> Art Silk Sherwani in Off White</li><li> This Readymade attire is Enhanced with Buttons, Pockets, Chikankari, Thread and Sequins Work. Crafted in Chinese Collar Neck and Full Sleeve</li><li> Available with an Art Silk Pant in Off White and a Faux Georgette Jacket with Satin Lining in Off White</li><li> Do note: 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>USDtype_new:Sherwanicolorfam:Whitefabric:Art SilkWhiteArt SilkSherwani11%-20%MenReady to Ship, Within 2 days, Within 7 days, Within 10 days, Within 15 days, More than 15 DaysReadymadeWeddingMenswearButtons, Sequins, Thread Work, Traditional48