diff --git a/core/capabilities/ccip/ccipevm/gas_helpers_test.go b/core/capabilities/ccip/ccipevm/gas_helpers_test.go
new file mode 100644
index 0000000000..f7897898fb
--- /dev/null
+++ b/core/capabilities/ccip/ccipevm/gas_helpers_test.go
@@ -0,0 +1,157 @@
+package ccipevm
+
+import (
+	"math/big"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/stretchr/testify/assert"
+
+	"github.com/smartcontractkit/chainlink-common/pkg/types/ccipocr3"
+)
+
+func Test_calculateMessageMaxGas(t *testing.T) {
+	type args struct {
+		dataLen   int
+		numTokens int
+		extraArgs []byte
+	}
+	tests := []struct {
+		name string
+		args args
+		want uint64
+	}{
+		{
+			name: "base",
+			args: args{dataLen: 5, numTokens: 2, extraArgs: makeExtraArgsV1(200_000)},
+			want: 1_022_264,
+		},
+		{
+			name: "large",
+			args: args{dataLen: 1000, numTokens: 1000, extraArgs: makeExtraArgsV1(200_000)},
+			want: 346_677_520,
+		},
+		{
+			name: "overheadGas test 1",
+			args: args{dataLen: 0, numTokens: 0, extraArgs: makeExtraArgsV1(200_000)},
+			want: 319_920,
+		},
+		{
+			name: "overheadGas test 2",
+			args: args{dataLen: len([]byte{0x0, 0x0, 0x0, 0x0, 0x0, 0x0}), numTokens: 1, extraArgs: makeExtraArgsV1(200_000)},
+			want: 675_948,
+		},
+		{
+			name: "allowOOO set to true makes no difference to final gas estimate",
+			args: args{dataLen: 5, numTokens: 2, extraArgs: makeExtraArgsV2(200_000, true)},
+			want: 1_022_264,
+		},
+		{
+			name: "allowOOO set to false makes no difference to final gas estimate",
+			args: args{dataLen: 5, numTokens: 2, extraArgs: makeExtraArgsV2(200_000, false)},
+			want: 1_022_264,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			msg := ccipocr3.Message{
+				Data:         make([]byte, tt.args.dataLen),
+				TokenAmounts: make([]ccipocr3.RampTokenAmount, tt.args.numTokens),
+				ExtraArgs:    tt.args.extraArgs,
+			}
+			ep := EstimateProvider{}
+			got := ep.CalculateMessageMaxGas(msg)
+			t.Log(got)
+			assert.Equalf(t, tt.want, got, "calculateMessageMaxGas(%v, %v)", tt.args.dataLen, tt.args.numTokens)
+		})
+	}
+}
+
+// TestCalculateMaxGas is taken from the ccip repo where the CalculateMerkleTreeGas and CalculateMessageMaxGas values
+// are combined to one function.
+func TestCalculateMaxGas(t *testing.T) {
+	tests := []struct {
+		name           string
+		numRequests    int
+		dataLength     int
+		numberOfTokens int
+		extraArgs      []byte
+		want           uint64
+	}{
+		{
+			name:           "maxGasOverheadGas 1",
+			numRequests:    6,
+			dataLength:     0,
+			numberOfTokens: 0,
+			extraArgs:      makeExtraArgsV1(200_000),
+			want:           322_992,
+		},
+		{
+			name:           "maxGasOverheadGas 2",
+			numRequests:    3,
+			dataLength:     len([]byte{0x0, 0x0, 0x0, 0x0, 0x0, 0x0}),
+			numberOfTokens: 1,
+			extraArgs:      makeExtraArgsV1(200_000),
+			want:           678_508,
+		},
+		{
+			name:           "v2 extra args",
+			numRequests:    3,
+			dataLength:     len([]byte{0x0, 0x0, 0x0, 0x0, 0x0, 0x0}),
+			numberOfTokens: 1,
+			extraArgs:      makeExtraArgsV2(200_000, true),
+			want:           678_508,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			msg := ccipocr3.Message{
+				Data:         make([]byte, tt.dataLength),
+				TokenAmounts: make([]ccipocr3.RampTokenAmount, tt.numberOfTokens),
+				ExtraArgs:    tt.extraArgs,
+			}
+			ep := EstimateProvider{}
+
+			gotTree := ep.CalculateMerkleTreeGas(tt.numRequests)
+			gotMsg := ep.CalculateMessageMaxGas(msg)
+			t.Log("want", tt.want, "got", gotTree+gotMsg)
+			assert.Equal(t, tt.want, gotTree+gotMsg)
+		})
+	}
+}
+
+func makeExtraArgsV1(gasLimit uint64) []byte {
+	// extra args is the tag followed by the gas limit abi-encoded.
+	var extraArgs []byte
+	extraArgs = append(extraArgs, evmExtraArgsV1Tag...)
+	gasLimitBytes := new(big.Int).SetUint64(gasLimit).Bytes()
+	// pad from the left to 32 bytes
+	gasLimitBytes = common.LeftPadBytes(gasLimitBytes, 32)
+	extraArgs = append(extraArgs, gasLimitBytes...)
+	return extraArgs
+}
+
+func makeExtraArgsV2(gasLimit uint64, allowOOO bool) []byte {
+	// extra args is the tag followed by the gas limit and allowOOO abi-encoded.
+	var extraArgs []byte
+	extraArgs = append(extraArgs, evmExtraArgsV2Tag...)
+	gasLimitBytes := new(big.Int).SetUint64(gasLimit).Bytes()
+	// pad from the left to 32 bytes
+	gasLimitBytes = common.LeftPadBytes(gasLimitBytes, 32)
+
+	// abi-encode allowOOO
+	var allowOOOBytes []byte
+	if allowOOO {
+		allowOOOBytes = append(allowOOOBytes, 1)
+	} else {
+		allowOOOBytes = append(allowOOOBytes, 0)
+	}
+	// pad from the left to 32 bytes
+	allowOOOBytes = common.LeftPadBytes(allowOOOBytes, 32)
+
+	extraArgs = append(extraArgs, gasLimitBytes...)
+	extraArgs = append(extraArgs, allowOOOBytes...)
+	return extraArgs
+}