diff --git a/README.md b/README.md
index a3fcdc1..9190705 100644
--- a/README.md
+++ b/README.md
@@ -15,7 +15,7 @@ Retrier objects are intended to be re-used, which means you define them once and
 ```go
 // create a new retrier that will try a maximum of five times, with
 // an initial delay of 100 ms and a maximum delay of 1 second
-retrier := retry.NewRetrier(5, 100, 1000)
+retrier := retry.NewRetrier(5, 100 * time.Millisecond, time.Second)
 
 err := retrier.Run(func() error {
     resp, err := http.Get("http://golang.org")
@@ -41,7 +41,7 @@ if err != nil {
 ```go
 // create a new retrier that will try a maximum of five times, with
 // an initial delay of 100 ms and a maximum delay of 1 second
-retrier := retry.NewRetrier(5, 100, 1000)
+retrier := retry.NewRetrier(5, 100 * time.Millisecond, time.Second)
 ctx, cancel := context.WithTimeout(context.Background(), 10*time.Millisecond)
 defer cancel()
 
diff --git a/retry.go b/retry.go
index 04110ef..c40ea24 100644
--- a/retry.go
+++ b/retry.go
@@ -9,9 +9,9 @@ import (
 
 // Default backoff
 const (
-	DefaultMaxTries       = 5
-	DefaultInitialDelayMS = 200
-	DefaultMaxDelayMS     = 1000
+	DefaultMaxTries     = 5
+	DefaultInitialDelay = time.Millisecond * 200
+	DefaultMaxDelay     = time.Millisecond * 1000
 )
 
 // Retrier retries code blocks with or without context using an exponential
@@ -19,21 +19,21 @@ const (
 // which means it is safe to create and use concurrently.
 type Retrier struct {
 	maxTries     int
-	initialDelay int
-	maxDelay     int
+	initialDelay time.Duration
+	maxDelay     time.Duration
 }
 
 // NewRetrier returns a retrier for retrying functions with expoential backoff.
 // If any of the values are <= 0, they will be set to their respective defaults.
-func NewRetrier(maxTries, initialDelay, maxDelay int) *Retrier {
+func NewRetrier(maxTries int, initialDelay, maxDelay time.Duration) *Retrier {
 	if maxTries <= 0 {
 		maxTries = DefaultMaxTries
 	}
 	if initialDelay <= 0 {
-		initialDelay = DefaultInitialDelayMS
+		initialDelay = DefaultInitialDelay
 	}
 	if maxDelay <= 0 {
-		maxDelay = DefaultMaxDelayMS
+		maxDelay = DefaultMaxDelay
 	}
 	return &Retrier{maxTries, initialDelay, maxDelay}
 }
@@ -122,10 +122,10 @@ func (t terminalError) Error() string {
 	return t.e.Error()
 }
 
-func getnextBackoff(attempts, initialDelay, maxDelay int) time.Duration {
+func getnextBackoff(attempts int, initialDelay, maxDelay time.Duration) time.Duration {
 	return min(
-		time.Duration(maxDelay)*time.Millisecond,
-		time.Duration(randInt63n(int64(initialDelay)*(1<<uint(attempts))))*time.Millisecond,
+		maxDelay,
+		time.Duration(randInt63n(int64(initialDelay)*(1<<uint(attempts)))),
 	)
 }
 
diff --git a/retry_test.go b/retry_test.go
index ac429e6..ae62fce 100644
--- a/retry_test.go
+++ b/retry_test.go
@@ -20,7 +20,7 @@ func TestBackoffBacksOff(t *testing.T) {
 		tries := 0
 		start := time.Now()
 		var last time.Time
-		retrier := NewRetrier(5, 50, 50)
+		retrier := NewRetrier(5, 50*time.Millisecond, 50*time.Millisecond)
 		err := retrier.Run(func() error {
 			tries++
 			last = time.Now()
@@ -41,7 +41,7 @@ func TestBackoffBacksOff(t *testing.T) {
 		tries := 0
 		start := time.Now()
 		var last time.Time
-		retrier := NewRetrier(5, 50, 50)
+		retrier := NewRetrier(5, 50*time.Millisecond, 50*time.Millisecond)
 		err := retrier.RunContext(context.Background(), func(ctx context.Context) error {
 			tries++
 			last = time.Now()
@@ -63,7 +63,7 @@ func TestBackoffBacksOff(t *testing.T) {
 func TestEventualSuccessSucceedsTransparently(t *testing.T) {
 	t.Run("r.Run", func(t *testing.T) {
 		tries := 0
-		retrier := NewRetrier(5, 50, 50)
+		retrier := NewRetrier(5, 50*time.Millisecond, 50*time.Millisecond)
 		err := retrier.Run(func() error {
 			tries++
 			if tries == 2 {
@@ -80,7 +80,7 @@ func TestEventualSuccessSucceedsTransparently(t *testing.T) {
 	})
 	t.Run("r.RunContext", func(t *testing.T) {
 		tries := 0
-		retrier := NewRetrier(5, 50, 50)
+		retrier := NewRetrier(5, 50*time.Millisecond, 50*time.Millisecond)
 		err := retrier.RunContext(context.Background(), func(ctx context.Context) error {
 			tries++
 			if tries == 2 {
@@ -102,7 +102,7 @@ func TestRunContextExitsEarlyWhenContextCanceled(t *testing.T) {
 	var wg sync.WaitGroup
 	tries := 0
 	ctx, canceler := context.WithCancel(context.Background())
-	retrier := NewRetrier(5, 50, 50)
+	retrier := NewRetrier(5, 50*time.Millisecond, 50*time.Millisecond)
 
 	wg.Add(1)
 	go func() {
@@ -130,7 +130,7 @@ func TestRunContextExitsEarlyWhenContextCanceled(t *testing.T) {
 func TestStopStopsImmediately(t *testing.T) {
 	t.Run("r.Run", func(t *testing.T) {
 		tries := 0
-		retrier := NewRetrier(5, 50, 50)
+		retrier := NewRetrier(5, 50*time.Millisecond, 50*time.Millisecond)
 		err := retrier.Run(func() error {
 			tries++
 			return Stop(errTest)
@@ -145,7 +145,7 @@ func TestStopStopsImmediately(t *testing.T) {
 	})
 	t.Run("r.RunContext", func(t *testing.T) {
 		tries := 0
-		retrier := NewRetrier(5, 50, 50)
+		retrier := NewRetrier(5, 50*time.Millisecond, 50*time.Millisecond)
 		err := retrier.RunContext(context.Background(), func(ctx context.Context) error {
 			tries++
 			return Stop(errTest)
@@ -165,11 +165,11 @@ func TestRetrierGetsDefaultsIfLessThanZero(t *testing.T) {
 	if r.maxTries != DefaultMaxTries {
 		t.Errorf("expected maxTries to be %d, got %d", DefaultMaxTries, r.maxTries)
 	}
-	if r.initialDelay != DefaultInitialDelayMS {
-		t.Errorf("expected initialDelay to be %d, got %d", DefaultInitialDelayMS, r.initialDelay)
+	if r.initialDelay != DefaultInitialDelay {
+		t.Errorf("expected initialDelay to be %d, got %d", DefaultInitialDelay, r.initialDelay)
 	}
-	if r.maxDelay != DefaultMaxDelayMS {
-		t.Errorf("expected maxDelay to be %d, got %d", DefaultMaxDelayMS, r.maxDelay)
+	if r.maxDelay != DefaultMaxDelay {
+		t.Errorf("expected maxDelay to be %d, got %d", DefaultMaxDelay, r.maxDelay)
 	}
 }
 
@@ -186,7 +186,7 @@ type myErrorType struct{}
 func (m myErrorType) Error() string { return "myErrorType" }
 
 func TestTerminalErrorRetainsOriginalError(t *testing.T) {
-	retrier := NewRetrier(5, 50, 50)
+	retrier := NewRetrier(5, 50*time.Millisecond, 50*time.Millisecond)
 	tries := 0
 	err := retrier.Run(func() error {
 		tries++
@@ -203,7 +203,7 @@ func TestTerminalErrorRetainsOriginalError(t *testing.T) {
 }
 
 func ExampleRetrier_Run() {
-	retrier := NewRetrier(5, 50, 50)
+	retrier := NewRetrier(5, 50*time.Millisecond, 50*time.Millisecond)
 	err := retrier.Run(func() error {
 		resp, err := http.Get("http://golang.org")
 		switch {
@@ -220,7 +220,7 @@ func ExampleRetrier_Run() {
 }
 
 func ExampleRetrier_RunContext_output() {
-	retrier := NewRetrier(5, 50, 50)
+	retrier := NewRetrier(5, 50*time.Millisecond, 50*time.Millisecond)
 	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Millisecond)
 	defer cancel()