This research is a research development (Research and Development) that aims to determine the feasibility of LKPD Mathematics products as well as the supporting and inhibiting factors of using LKPD. This study uses the Borg and Gall development model. The instruments used were tests, interviews, and questionnaires. There are 3 types of questionnaires used, namely expert validation questionnaires, student response questionnaires, and teacher response questionnaires. The results of the validation that have been carried out by the three validators obtained an overall average value of 4.16 with valid criteria. The LKPD trials were carried out by the Delikan learning steps (listen, see, and do). The average score of the students' questionnaire response was 4.58 with very good criteria. The teacher response questionnaire to the mathematics LKPD obtained a result of 4.2 with a good category. The use of LKPD received a very good response from students because the use of calculators was something new, but some students did not understand the concept of multiplication and long division so they needed guidance from the teacher. LKPD Mathematics of the circumference and area of a flat shape using a calculator with Delikan learning in Class IV SD UMP is said to be feasible and can be used as an alternative teaching material to improve skills in calculating the circumference and area of a flat shape using a calculator calculating tool.