diff --git a/README.md b/README.md
index bd90ef0..076c379 100644
--- a/README.md
+++ b/README.md
@@ -1 +1,15 @@
-# java-calculator-precourse
\ No newline at end of file
+# java-calculator-precourse
+
+## Feature Details
+- CLI I/O
+- 구분자 추출
+- 수식 계산
+
+## Code Flow
+- 수식 입력
+- (커스텀 구분자가 있다면) 커스텀 구분자 추출
+- 수식 구성
+- 수식 계산
+
+## Design Pattern
+- Hexagonal Architecture 도입
diff --git a/src/main/java/calculator/Application.java b/src/main/java/calculator/Application.java
index 573580f..1045911 100644
--- a/src/main/java/calculator/Application.java
+++ b/src/main/java/calculator/Application.java
@@ -1,7 +1,13 @@
 package calculator;
 
+import calculator.adapter.in.InputTerminal;
+import calculator.adapter.out.OutputTerminal;
+import calculator.application.service.CalculatorService;
+
 public class Application {
     public static void main(String[] args) {
         // TODO: 프로그램 구현
+        CalculatorService calculatorService = new CalculatorService(new OutputTerminal(), new InputTerminal());
+        calculatorService.run();
     }
 }
diff --git a/src/main/java/calculator/adapter/in/InputTerminal.java b/src/main/java/calculator/adapter/in/InputTerminal.java
new file mode 100644
index 0000000..1f6a0a0
--- /dev/null
+++ b/src/main/java/calculator/adapter/in/InputTerminal.java
@@ -0,0 +1,10 @@
+package calculator.adapter.in;
+
+import calculator.application.port.inport.GetExpressionUserCase;
+import camp.nextstep.edu.missionutils.Console;
+
+public class InputTerminal implements GetExpressionUserCase {
+    public String getExpression() {
+        return Console.readLine();
+    }
+}
diff --git a/src/main/java/calculator/application/port/inport/GetExpressionUserCase.java b/src/main/java/calculator/application/port/inport/GetExpressionUserCase.java
new file mode 100644
index 0000000..0414ce6
--- /dev/null
+++ b/src/main/java/calculator/application/port/inport/GetExpressionUserCase.java
@@ -0,0 +1,5 @@
+package calculator.application.port.inport;
+
+public interface GetExpressionUserCase {
+    String getExpression();
+}
diff --git a/src/main/java/calculator/application/port/outport/ResultTerminal.java b/src/main/java/calculator/application/port/outport/ResultTerminal.java
new file mode 100644
index 0000000..34015cd
--- /dev/null
+++ b/src/main/java/calculator/application/port/outport/ResultTerminal.java
@@ -0,0 +1,9 @@
+package calculator.application.port.outport;
+
+import calculator.domain.enums.MessageConstant;
+
+public interface ResultTerminal {
+    void printMessage(MessageConstant message);
+    void printResult(int result);
+    void handleException(RuntimeException e);
+}
diff --git a/src/main/java/calculator/application/service/CalculatorService.java b/src/main/java/calculator/application/service/CalculatorService.java
new file mode 100644
index 0000000..56850dd
--- /dev/null
+++ b/src/main/java/calculator/application/service/CalculatorService.java
@@ -0,0 +1,28 @@
+package calculator.application.service;
+
+import calculator.application.port.inport.GetExpressionUserCase;
+import calculator.application.port.outport.ResultTerminal;
+import calculator.domain.Expression;
+import calculator.domain.enums.MessageConstant;
+
+public class CalculatorService {
+    private final ResultTerminal resultTerminal;
+    private final GetExpressionUserCase getExpressionUserCase;
+
+    public CalculatorService(ResultTerminal resultTerminal, GetExpressionUserCase getExpressionUserCase) {
+        this.resultTerminal = resultTerminal;
+        this.getExpressionUserCase = getExpressionUserCase;
+    }
+
+    public void run() {
+        try {
+            resultTerminal.printMessage(MessageConstant.START_GUIDE_MESSAGE);
+            String line = getExpressionUserCase.getExpression();
+            Expression expression = new Expression(line);
+            int result = expression.calculate();
+            resultTerminal.printResult(result);
+        } catch (RuntimeException e) {
+            resultTerminal.handleException(e);
+        }
+    }
+}
diff --git a/src/main/java/calculator/domain/Expression.java b/src/main/java/calculator/domain/Expression.java
new file mode 100644
index 0000000..83e0841
--- /dev/null
+++ b/src/main/java/calculator/domain/Expression.java
@@ -0,0 +1,47 @@
+package calculator.domain;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+import java.util.stream.Stream;
+
+public class Expression {
+    private final List<Integer> operands;
+    private static final String CUSTOM_SEPARATOR_REGEX = "^//(.)\\\\n(.*)";
+    private static final String EXPRESSION_REGEX_BASE = "([0-9]+)[[%s]+([0-9]+)]*";
+
+    public Expression(String expressionLine) {
+        operands = new ArrayList<>();
+
+        String separator = "[,:]";
+        String expressionBody = expressionLine;
+
+        Matcher matcher = Pattern.compile(CUSTOM_SEPARATOR_REGEX).matcher(expressionBody);
+        if (matcher.find()) {
+            separator = String.format("[,:%s]", Pattern.quote(matcher.group(1)));
+            expressionBody = matcher.group(2);
+        }
+
+        validateExpression(expressionBody, separator);
+        parseOperand(expressionBody, separator);
+    }
+
+    private void validateExpression(String expressionBody, String separator) {
+        String fullRegex = String.format(EXPRESSION_REGEX_BASE, separator);
+        if (!expressionBody.matches(fullRegex)) {
+            throw new IllegalArgumentException("잘못된 수식입니다: " + expressionBody);
+        }
+    }
+
+    private void parseOperand(String body, String separatorRegex) {
+        Stream.of(body.split(separatorRegex))
+                .map(Integer::parseInt)
+                .forEach(operands::add);
+    }
+
+
+    public int calculate() {
+        return operands.stream().reduce(0, Math::addExact);
+    }
+}
diff --git a/src/main/java/calculator/domain/enums/MessageConstant.java b/src/main/java/calculator/domain/enums/MessageConstant.java
new file mode 100644
index 0000000..aac192d
--- /dev/null
+++ b/src/main/java/calculator/domain/enums/MessageConstant.java
@@ -0,0 +1,15 @@
+package calculator.domain.enums;
+
+public enum MessageConstant {
+    START_GUIDE_MESSAGE("덧셈할 문자열을 입력해 주세요."),
+    RESULT_MESSAGE("결과 : ");
+
+    private String message;
+
+    MessageConstant(String message) {
+        this.message = message;
+    }
+    public String getMessage() {
+        return message;
+    }
+}
diff --git a/src/test/java/calculator/ApplicationTest.java b/src/test/java/calculator/ApplicationTest.java
index 93771fb..af087ec 100644
--- a/src/test/java/calculator/ApplicationTest.java
+++ b/src/test/java/calculator/ApplicationTest.java
@@ -8,19 +8,100 @@
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 class ApplicationTest extends NsTest {
+
+    @Test
+    void exampleTest() {
+        assertSimpleTest(() -> {
+            run("1,2:3");
+            assertThat(output()).contains("결과 : 6");
+        });
+    }
+
+    @Test
+    void constantExpressionTest() {
+        assertSimpleTest(() -> {
+            run("5");
+            assertThat(output()).contains("결과 : 5");
+        });
+    }
+
+    @Test
+    void customSeparatorTest() {
+        assertSimpleTest(() -> {
+            run("//;\\n3;4:5");
+            assertThat(output()).contains("결과 : 12");
+        });
+    }
+
+    @Test
+    void intOverflowTest() {
+        assertSimpleTest(() ->
+                assertThatThrownBy(() -> runException("20000000000"))
+                        .isInstanceOf(IllegalArgumentException.class)
+        );
+    }
+
+    @Test
+    void longOverflowTest() {
+        assertSimpleTest(() ->
+                assertThatThrownBy(() -> runException("50000000000000000000"))
+                        .isInstanceOf(IllegalArgumentException.class)
+        );
+    }
+
+    @Test
+    void severalCustomSeparatorTest() {
+        assertSimpleTest(() ->
+                assertThatThrownBy(() -> runException("//^&\\n3^4&5"))
+                        .isInstanceOf(IllegalArgumentException.class)
+        );
+    }
+
+    @Test
+    void numberSeparatorTest() {
+        assertSimpleTest(() ->
+                assertThatThrownBy(() -> runException("//3\\n53:43"))
+                        .isInstanceOf(IllegalArgumentException.class)
+        );
+    }
+
+    @Test
+    void emptyExpressionTest() {
+        assertSimpleTest(() ->
+                assertThatThrownBy(() -> runException(""))
+                        .isInstanceOf(IllegalArgumentException.class)
+        );
+    }
+
+    @Test
+    void intAddingOverflowTest() {
+        assertSimpleTest(() ->
+                assertThatThrownBy(() -> runException("2000000000:2000000000"))
+                        .isInstanceOf(IllegalArgumentException.class)
+        );
+    }
+
+    @Test
+    void longAddingOverflowTest() {
+        assertSimpleTest(() ->
+                assertThatThrownBy(() -> runException("5000000000000000000:5000000000000000000"))
+                        .isInstanceOf(IllegalArgumentException.class)
+        );
+    }
+
     @Test
-    void 커스텀_구분자_사용() {
+    void escapeCharTest() {
         assertSimpleTest(() -> {
-            run("//;\\n1");
-            assertThat(output()).contains("결과 : 1");
+            run("//\\\\n3\\4\\5");
+            assertThat(output()).contains("결과 : 12");
         });
     }
 
     @Test
-    void 예외_테스트() {
+    void emptyValueTest() {
         assertSimpleTest(() ->
-            assertThatThrownBy(() -> runException("-1,2,3"))
-                .isInstanceOf(IllegalArgumentException.class)
+                assertThatThrownBy(() -> runException("//*\\n3**:,,4"))
+                        .isInstanceOf(IllegalArgumentException.class)
         );
     }
 
diff --git a/src/test/java/calculator/ExpressionTest.java b/src/test/java/calculator/ExpressionTest.java
new file mode 100644
index 0000000..d186d87
--- /dev/null
+++ b/src/test/java/calculator/ExpressionTest.java
@@ -0,0 +1,60 @@
+package calculator;
+
+import calculator.domain.Expression;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class ExpressionTest {
+
+    @Test
+    void 기본_구분자_쉼표_콜론으로_계산() {
+        Expression expr = new Expression("1,2:3");
+        assertEquals(6, expr.calculate());
+    }
+
+    @Test
+    void 커스텀_구분자_세미콜론으로_계산() {
+        Expression expr = new Expression("//;\\n1;2;3");
+        assertEquals(6, expr.calculate());
+    }
+
+    @Test
+    void 커스텀_구분자_점으로_계산() {
+        Expression expr = new Expression("//.\\n4.5:6");
+        assertEquals(15, expr.calculate());
+    }
+
+    @Test
+    void 커스텀_구분자와_기본_구분자_혼합() {
+        Expression expr = new Expression("//|\\n7|8,9:10");
+        assertEquals(34, expr.calculate());
+    }
+
+    @Test
+    void 유효하지_않은_표현식_예외() {
+        assertThrows(IllegalArgumentException.class, () -> {
+            new Expression("1,,2:3");
+        });
+    }
+
+    @Test
+    void 커스텀_정의된_구분자가_아닌_문자_포함시_예외() {
+        assertThrows(IllegalArgumentException.class, () -> {
+            new Expression("//;\\n1;2-3");
+        });
+    }
+
+    @Test
+    void 숫자가_아닌_문자가_포함되면_예외() {
+        assertThrows(IllegalArgumentException.class, () -> {
+            new Expression("1,a:3");
+        });
+    }
+
+    @Test
+    void 한자리_숫자가_아닌_수() {
+        Expression expr = new Expression("1,10,100,3000");
+        assertEquals(3111, expr.calculate());
+    }
+}