diff --git a/poker/constants.py b/poker/constants.py
index 04a8b34..e0a7348 100644
--- a/poker/constants.py
+++ b/poker/constants.py
@@ -3,6 +3,21 @@ from enum import IntEnum, auto
 from poker.utils.enum import AutoName
 
 
+class Rank(IntEnum):
+    """Poker rank enum."""
+
+    ROYAL_FLUSH = 1
+    STRAIGHT_FLUSH = 2
+    FOUR_OF_A_KIND = 3
+    FULL_HOUSE = 4
+    FLUSH = 5
+    STRAIGHT = 6
+    THREE_OF_A_KIND = 7
+    TWO_PAIR = 8
+    PAIR = 9
+    HIGH_CARD = 10
+
+
 class Suit(AutoName):
     """Card suit enum."""
 
@@ -15,7 +30,6 @@ class Suit(AutoName):
 class Value(IntEnum):
     """Card value enum."""
 
-    ACE = 1
     TWO = 2
     THREE = 3
     FOUR = 4
@@ -28,3 +42,12 @@ class Value(IntEnum):
     JACK = 11
     QUEEN = 12
     KING = 13
+    ACE = 14
+
+    def __str__(self) -> str:
+        """Return string representation."""
+        if self.value in [1, 11, 12, 13]:
+            out: str = self.name.lower()
+        else:
+            out = str(self.value)
+        return out
diff --git a/poker/models.py b/poker/models.py
index 1d6af05..bbb474c 100644
--- a/poker/models.py
+++ b/poker/models.py
@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+from collections import Counter
+
 from pydantic import BaseModel, validator
 
 from poker.constants import Rank, Suit, Value
@@ -43,6 +45,11 @@ class Hand(BaseModel):
             raise ValueError("Hand must have five cards.")
         return cards
 
+    @property
+    def value_counts(self) -> list[tuple[Value, int]]:
+        """Return count of each card value in hand."""
+        return Counter([card.value for card in self.cards]).most_common()
+
 
 class RankedHand(Hand):
     """Ranked hand  domain model class."""
diff --git a/poker/rank/__init__.py b/poker/rank/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/poker/rank/descriptions.py b/poker/rank/descriptions.py
new file mode 100644
index 0000000..e69de29
diff --git a/poker/rank/hands.py b/poker/rank/hands.py
new file mode 100644
index 0000000..8764ce9
--- /dev/null
+++ b/poker/rank/hands.py
@@ -0,0 +1,110 @@
+from poker.constants import Rank, Value
+from poker.models import Card, Hand
+
+
+def _is_flush(cards: list[Card]) -> bool:
+    """Calculate whether hand is a flush."""
+    return len(set(card.suit for card in cards)) == 1
+
+
+def _is_straight(cards: list[Card]) -> bool:
+    """Calculate whether hand is a straight."""
+    card_values = sorted([card.value for card in cards])
+
+    # If card values are not unique it is not a straight
+    if len(set(card_values)) != len(card_values):
+        return False
+
+    # Check for a ace low straight
+    if card_values == [Value.TWO, Value.THREE, Value.FOUR, Value.FIVE, Value.ACE]:
+        return True
+
+    # If all card differences are 1 it is a straight
+    diffs = [second - first for first, second in zip(card_values[:-1], card_values[1:])]
+    if set(diffs) == {1}:
+        return True
+
+    return False
+
+
+def is_royal_flush(hand: Hand) -> bool:
+    """Calculate whether hand a royal flush."""
+    if not _is_flush(hand.cards):
+        return False
+
+    values = [card.value for card in hand.cards]
+    return all(
+        value in values
+        for value in [Value.ACE, Value.KING, Value.QUEEN, Value.JACK, Value.TEN]
+    )
+
+
+def is_straight_flush(hand: Hand) -> bool:
+    """Calculate whether hand a straight flush."""
+    return _is_straight(hand.cards) and _is_flush(hand.cards)
+
+
+def is_four_of_a_kind(hand: Hand) -> bool:
+    """Calculate whether hand has four of a kind."""
+    return hand.value_counts[0][1] == 4
+
+
+def is_full_house(hand: Hand) -> bool:
+    """Calculate whether hand is a full house."""
+    return hand.value_counts[0][1] == 3 and hand.value_counts[1][1] == 2
+
+
+def is_flush(hand: Hand) -> bool:
+    """Calculate whether hand is a flush."""
+    return _is_flush(hand.cards) and not _is_straight(hand.cards)
+
+
+def is_straight(hand: Hand) -> bool:
+    """Calculate whether hand is a flush."""
+    return _is_straight(hand.cards) and not _is_flush(hand.cards)
+
+
+def is_three_of_a_kind(hand: Hand) -> bool:
+    """Calculate whether hand is a full house."""
+    return (
+        hand.value_counts[0][1] == 3
+        and hand.value_counts[1][1] == 1
+        and hand.value_counts[2][1] == 1
+    )
+
+
+def is_two_pair(hand: Hand) -> bool:
+    """Calculate whether hand is a two pair."""
+    return hand.value_counts[0][1] == 2 and hand.value_counts[1][1] == 2
+
+
+def is_pair(hand: Hand) -> bool:
+    """Calculate whether hand is a pair."""
+    return hand.value_counts[0][1] == 2 and hand.value_counts[1][1] == 1
+
+
+def get_rank(hand: Hand) -> Rank:
+    """Get hand rank.
+
+    TODO: Use a factory pattern to avoid this huge flow control.
+    """
+    if is_royal_flush(hand):
+        return Rank.ROYAL_FLUSH
+    elif is_straight_flush(hand):
+        return Rank.STRAIGHT_FLUSH
+    elif is_four_of_a_kind(hand):
+        return Rank.FOUR_OF_A_KIND
+    elif is_full_house(hand):
+        return Rank.FULL_HOUSE
+    elif is_flush(hand):
+        return Rank.FLUSH
+    elif is_straight(hand):
+        return Rank.STRAIGHT
+    elif is_three_of_a_kind(hand):
+        return Rank.THREE_OF_A_KIND
+    elif is_two_pair(hand):
+        return Rank.TWO_PAIR
+    elif is_pair(hand):
+        return Rank.PAIR
+    else:
+        return Rank.HIGH_CARD
diff --git a/pyproject.toml b/pyproject.toml
index 5565627..5c4b912 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "poker"
-version = "0.2.4"
+version = "1.0.0"
 description = "Single poker hand ranking service."
 authors = ["Paul Harrison"]
 readme = "README.md"
diff --git a/tests/test_rank.py b/tests/test_rank.py
new file mode 100644
index 0000000..f504a3e
--- /dev/null
+++ b/tests/test_rank.py
@@ -0,0 +1,446 @@
+from itertools import cycle
+
+import pytest
+
+from poker.constants import Suit, Value
+from poker.models import Card, Hand
+from poker.rank.hands import (
+    _is_flush,
+    _is_straight,
+    is_flush,
+    is_four_of_a_kind,
+    is_full_house,
+    is_pair,
+    is_royal_flush,
+    is_straight,
+    is_straight_flush,
+    is_three_of_a_kind,
+    is_two_pair,
+)
+from tests.conftest import Factory
+
+
+@pytest.mark.parametrize(
+    "suits,expected",
+    [
+        ([Suit.CLUBS, Suit.DIAMONDS, Suit.SPADES, Suit.HEARTS, Suit.CLUBS], False),
+        ([Suit.CLUBS, Suit.CLUBS, Suit.CLUBS, Suit.CLUBS, Suit.CLUBS], True),
+    ],
+    ids=[
+        "non-unique",
+        "unique",
+    ],
+)
+def test__is_flush(
+    card_factory: Factory[Card], suits: list[Suit], expected: bool
+) -> None:
+    result = _is_flush([card_factory(suit=suit) for suit in suits])
+
+    if expected:
+        assert result
+    else:
+        assert not result
+
+
+@pytest.mark.parametrize(
+    "values,expected",
+    [
+        ([Value.TWO, Value.TWO, Value.THREE, Value.FOUR, Value.FIVE], False),
+        ([Value.THREE, Value.TWO, Value.ACE, Value.TEN, Value.KING], False),
+        ([Value.ACE, Value.TWO, Value.THREE, Value.FOUR, Value.FIVE], True),
+        ([Value.ACE, Value.KING, Value.TEN, Value.JACK, Value.QUEEN], True),
+        ([Value.THREE, Value.FIVE, Value.TWO, Value.FOUR, Value.SIX], True),
+    ],
+    ids=[
+        "non-unique",
+        "not-flush",
+        "low-ace",
+        "high-ace",
+        "middle-flush",
+    ],
+)
+def test__is_straight(
+    card_factory: Factory[Card], values: list[Value], expected: bool
+) -> None:
+    suits = cycle(Suit)
+    result = _is_straight(
+        [card_factory(suit=suit, value=value) for suit, value in zip(suits, values)]
+    )
+
+    if expected:
+        assert result
+    else:
+        assert not result
+
+
+@pytest.mark.parametrize(
+    "values,different_suits,expected",
+    [
+        ([Value.TWO, Value.TEN, Value.THREE, Value.FOUR, Value.FIVE], False, False),
+        ([Value.ACE, Value.KING, Value.TEN, Value.JACK, Value.QUEEN], False, True),
+        ([Value.ACE, Value.KING, Value.TEN, Value.JACK, Value.QUEEN], True, False),
+    ],
+    ids=[
+        "not-flush",
+        "royal-flush",
+        "flush-not-royal",
+    ],
+)
+def test_is_royal_flush(
+    card_factory: Factory[Card],
+    values: list[Value],
+    different_suits: bool,
+    expected: bool,
+) -> None:
+    suits = cycle(Suit)
+
+    if different_suits:
+        result = is_royal_flush(
+            Hand(
+                cards=[
+                    card_factory(suit=suit, value=value)
+                    for suit, value in zip(suits, values)
+                ]
+            )
+        )
+    else:
+        result = is_royal_flush(
+            Hand(cards=[card_factory(value=value) for value in values])
+        )
+
+    if expected:
+        assert result
+    else:
+        assert not result
+
+
+@pytest.mark.parametrize(
+    "values,different_suits,expected",
+    [
+        ([Value.TWO, Value.THREE, Value.FOUR, Value.FIVE, Value.SIX], True, False),
+        ([Value.TWO, Value.THREE, Value.FIVE, Value.SIX, Value.TEN], False, False),
+        ([Value.TWO, Value.THREE, Value.FOUR, Value.FIVE, Value.SIX], False, True),
+    ],
+    ids=[
+        "straight-only",
+        "flush-only",
+        "straight-flush",
+    ],
+)
+def test_is_straight_flush(
+    card_factory: Factory[Card],
+    values: list[Value],
+    different_suits: bool,
+    expected: bool,
+) -> None:
+    suits = cycle(Suit)
+
+    if different_suits:
+        result = is_straight_flush(
+            Hand(
+                cards=[
+                    card_factory(suit=suit, value=value)
+                    for suit, value in zip(suits, values)
+                ]
+            )
+        )
+    else:
+        result = is_straight_flush(
+            Hand(cards=[card_factory(value=value) for value in values])
+        )
+
+    if expected:
+        assert result
+    else:
+        assert not result
+
+
+@pytest.mark.parametrize(
+    "cards,expected",
+    [
+        (
+            [
+                Card(suit=Suit.CLUBS, value=Value.TWO),
+                Card(suit=Suit.DIAMONDS, value=Value.TWO),
+                Card(suit=Suit.HEARTS, value=Value.TWO),
+                Card(suit=Suit.SPADES, value=Value.TWO),
+                Card(suit=Suit.CLUBS, value=Value.THREE),
+            ],
+            True,
+        ),
+        (
+            [
+                Card(suit=Suit.CLUBS, value=Value.TEN),
+                Card(suit=Suit.DIAMONDS, value=Value.TWO),
+                Card(suit=Suit.HEARTS, value=Value.TWO),
+                Card(suit=Suit.SPADES, value=Value.TWO),
+                Card(suit=Suit.CLUBS, value=Value.THREE),
+            ],
+            False,
+        ),
+    ],
+    ids=[
+        "four-of-a-kind",
+        "not-four-of-a-kind",
+    ],
+)
+def test_is_four_of_a_kind(cards: list[Card], expected: bool) -> None:
+    result = is_four_of_a_kind(Hand(cards=cards))
+
+    if expected:
+        assert result
+    else:
+        assert not result
+
+
+@pytest.mark.parametrize(
+    "cards,expected",
+    [
+        (
+            [
+                Card(suit=Suit.CLUBS, value=Value.THREE),
+                Card(suit=Suit.DIAMONDS, value=Value.TWO),
+                Card(suit=Suit.HEARTS, value=Value.TWO),
+                Card(suit=Suit.SPADES, value=Value.TWO),
+                Card(suit=Suit.SPADES, value=Value.THREE),
+            ],
+            True,
+        ),
+        (
+            [
+                Card(suit=Suit.CLUBS, value=Value.TWO),
+                Card(suit=Suit.DIAMONDS, value=Value.TWO),
+                Card(suit=Suit.HEARTS, value=Value.TWO),
+                Card(suit=Suit.SPADES, value=Value.TWO),
+                Card(suit=Suit.CLUBS, value=Value.THREE),
+            ],
+            False,
+        ),
+    ],
+    ids=[
+        "full-house",
+        "not-full-house",
+    ],
+)
+def test_is_full_house(cards: list[Card], expected: bool) -> None:
+    result = is_full_house(Hand(cards=cards))
+
+    if expected:
+        assert result
+    else:
+        assert not result
+
+
+@pytest.mark.parametrize(
+    "values,different_suits,expected",
+    [
+        ([Value.TWO, Value.THREE, Value.FOUR, Value.FIVE, Value.SIX], True, False),
+        ([Value.TWO, Value.THREE, Value.FIVE, Value.SIX, Value.TEN], False, True),
+        ([Value.TWO, Value.THREE, Value.FOUR, Value.FIVE, Value.SIX], False, False),
+    ],
+    ids=[
+        "straight-only",
+        "flush-only",
+        "straight-flush",
+    ],
+)
+def test_is_flush(
+    card_factory: Factory[Card],
+    values: list[Value],
+    different_suits: bool,
+    expected: bool,
+) -> None:
+    suits = cycle(Suit)
+
+    if different_suits:
+        result = is_flush(
+            Hand(
+                cards=[
+                    card_factory(suit=suit, value=value)
+                    for suit, value in zip(suits, values)
+                ]
+            )
+        )
+    else:
+        result = is_flush(Hand(cards=[card_factory(value=value) for value in values]))
+
+    if expected:
+        assert result
+    else:
+        assert not result
+
+
+@pytest.mark.parametrize(
+    "values,different_suits,expected",
+    [
+        ([Value.TWO, Value.THREE, Value.FOUR, Value.FIVE, Value.SIX], True, True),
+        ([Value.TWO, Value.THREE, Value.FIVE, Value.SIX, Value.TEN], False, False),
+        ([Value.TWO, Value.THREE, Value.FOUR, Value.FIVE, Value.SIX], False, False),
+    ],
+    ids=[
+        "straight-only",
+        "flush-only",
+        "straight-flush",
+    ],
+)
+def test_is_straight(
+    card_factory: Factory[Card],
+    values: list[Value],
+    different_suits: bool,
+    expected: bool,
+) -> None:
+    suits = cycle(Suit)
+
+    if different_suits:
+        result = is_straight(
+            Hand(
+                cards=[
+                    card_factory(suit=suit, value=value)
+                    for suit, value in zip(suits, values)
+                ]
+            )
+        )
+    else:
+        result = is_straight(
+            Hand(cards=[card_factory(value=value) for value in values])
+        )
+
+    if expected:
+        assert result
+    else:
+        assert not result
+
+
+@pytest.mark.parametrize(
+    "cards,expected",
+    [
+        (
+            [
+                Card(suit=Suit.CLUBS, value=Value.THREE),
+                Card(suit=Suit.DIAMONDS, value=Value.TWO),
+                Card(suit=Suit.HEARTS, value=Value.TWO),
+                Card(suit=Suit.SPADES, value=Value.TWO),
+                Card(suit=Suit.SPADES, value=Value.THREE),
+            ],
+            False,
+        ),
+        (
+            [
+                Card(suit=Suit.CLUBS, value=Value.TWO),
+                Card(suit=Suit.DIAMONDS, value=Value.TWO),
+                Card(suit=Suit.HEARTS, value=Value.TWO),
+                Card(suit=Suit.SPADES, value=Value.ACE),
+                Card(suit=Suit.CLUBS, value=Value.THREE),
+            ],
+            True,
+        ),
+        (
+            [
+                Card(suit=Suit.CLUBS, value=Value.TWO),
+                Card(suit=Suit.DIAMONDS, value=Value.TWO),
+                Card(suit=Suit.HEARTS, value=Value.TEN),
+                Card(suit=Suit.SPADES, value=Value.ACE),
+                Card(suit=Suit.CLUBS, value=Value.THREE),
+            ],
+            False,
+        ),
+    ],
+    ids=["full-house", "three-of-a-kind", "not-three-of-a-kind"],
+)
+def test_is_three_of_a_kind(cards: list[Card], expected: bool) -> None:
+    result = is_three_of_a_kind(Hand(cards=cards))
+
+    if expected:
+        assert result
+    else:
+        assert not result
+
+
+@pytest.mark.parametrize(
+    "cards,expected",
+    [
+        (
+            [
+                Card(suit=Suit.CLUBS, value=Value.TWO),
+                Card(suit=Suit.DIAMONDS, value=Value.TWO),
+                Card(suit=Suit.HEARTS, value=Value.TWO),
+                Card(suit=Suit.SPADES, value=Value.THREE),
+                Card(suit=Suit.DIAMONDS, value=Value.THREE),
+            ],
+            False,
+        ),
+        (
+            [
+                Card(suit=Suit.CLUBS, value=Value.TWO),
+                Card(suit=Suit.DIAMONDS, value=Value.TWO),
+                Card(suit=Suit.HEARTS, value=Value.ACE),
+                Card(suit=Suit.SPADES, value=Value.ACE),
+                Card(suit=Suit.CLUBS, value=Value.THREE),
+            ],
+            True,
+        ),
+        (
+            [
+                Card(suit=Suit.CLUBS, value=Value.TWO),
+                Card(suit=Suit.DIAMONDS, value=Value.TWO),
+                Card(suit=Suit.HEARTS, value=Value.TWO),
+                Card(suit=Suit.SPADES, value=Value.ACE),
+                Card(suit=Suit.CLUBS, value=Value.THREE),
+            ],
+            False,
+        ),
+    ],
+    ids=["full-house", "two-pair", "three-of-a-kind"],
+)
+def test_is_two_pair(cards: list[Card], expected: bool) -> None:
+    result = is_two_pair(Hand(cards=cards))
+
+    if expected:
+        assert result
+    else:
+        assert not result
+
+
+@pytest.mark.parametrize(
+    "cards,expected",
+    [
+        (
+            [
+                Card(suit=Suit.CLUBS, value=Value.TWO),
+                Card(suit=Suit.DIAMONDS, value=Value.TWO),
+                Card(suit=Suit.HEARTS, value=Value.TWO),
+                Card(suit=Suit.SPADES, value=Value.THREE),
+                Card(suit=Suit.DIAMONDS, value=Value.THREE),
+            ],
+            False,
+        ),
+        (
+            [
+                Card(suit=Suit.CLUBS, value=Value.TWO),
+                Card(suit=Suit.DIAMONDS, value=Value.TWO),
+                Card(suit=Suit.HEARTS, value=Value.ACE),
+                Card(suit=Suit.SPADES, value=Value.ACE),
+                Card(suit=Suit.CLUBS, value=Value.THREE),
+            ],
+            False,
+        ),
+        (
+            [
+                Card(suit=Suit.CLUBS, value=Value.TWO),
+                Card(suit=Suit.DIAMONDS, value=Value.TWO),
+                Card(suit=Suit.HEARTS, value=Value.KING),
+                Card(suit=Suit.SPADES, value=Value.ACE),
+                Card(suit=Suit.CLUBS, value=Value.THREE),
+            ],
+            True,
+        ),
+    ],
+    ids=["full-house", "two-pair", "pair"],
+)
+def test_is_pair(cards: list[Card], expected: bool) -> None:
+    result = is_pair(Hand(cards=cards))
+
+    if expected:
+        assert result
+    else:
+        assert not result