No. Candidates are not allowed to carry calculators or any other electronic device in the examination centre.
Detailed information in this regard is available in the JEE Main 2020 Information Bulletin which furnished below for your reference.
JEE Main 2020 Calculator Use
Use of electronic devices like mobile phone, calculator etc. is NOT PERMITTED in JEE (Main) 2020
Candidates are also NOT allowed to carry Instrument/ Geometry/ Pencil box, Handbag, Purse, Any kind of Paper/ Stationery/ Textual material (printed or written material), Eatables and Water (loose or packed), Mobile Phone/ Ear Phone/ Microphone/ Pager, Calculator, Docu Pen, Slide Rules, Log Tables, Camera, Tape Recorder, Electronic Watches with facilities of calculator, any metallic item or electronic gadgets etc. in the examination Room/ Hall.
More detailed instructions will be printed on the admit card. After downloading it as per the schedule you should read all of them carefully.
Diabetic students will be allowed to carry eatables like sugar tablets/fruits (like banana/apple/ orange) and transparent water bottle to the examination hall. However, they will not be allowed to carry packed foods like chocolate / candy / sandwich etc.
Candidates must bring their own pencils, own geometry box set, erasers, colour pencils and crayons for the Aptitude Test of Paper-2.