diff --git a/docs/configuration/template_reference.md b/docs/configuration/template_reference.md
index 49a1e412f..92161f4c6 100644
--- a/docs/configuration/template_reference.md
+++ b/docs/configuration/template_reference.md
@@ -51,13 +51,13 @@ If functions are used in a pipeline, the pipeline value is passed as the last ar
 
 ### Numbers
 
-| Name          | Arguments     | Returns |  Notes    |
-| ------------- | --------------| --------| --------- |
-| humanize      | number        | string  | Converts a number to a more readable format, using [metric prefixes](https://en.wikipedia.org/wiki/Metric_prefix).
-| humanize1024  | number        | string  | Like `humanize`, but uses 1024 as the base rather than 1000. |
-| humanizeDuration | number     | string  | Converts a duration in seconds to a more readable format. |
-| humanizePercentage | number   | string  | Converts a ratio value to a fraction of 100. |
-| humanizeTimestamp | number    | string  | Converts a Unix timestamp in seconds to a more readable format. |
+| Name               | Arguments        | Returns |  Notes    |
+| ------------------ | -----------------| --------| --------- |
+| humanize           | number or string | string  | Converts a number to a more readable format, using [metric prefixes](https://en.wikipedia.org/wiki/Metric_prefix).
+| humanize1024       | number or string | string  | Like `humanize`, but uses 1024 as the base rather than 1000. |
+| humanizeDuration   | number or string | string  | Converts a duration in seconds to a more readable format. |
+| humanizePercentage | number or string | string  | Converts a ratio value to a fraction of 100. |
+| humanizeTimestamp  | number or string | string  | Converts a Unix timestamp in seconds to a more readable format. |
 
 Humanizing functions are intended to produce reasonable output for consumption
 by humans, and are not guaranteed to return the same results between Prometheus
diff --git a/template/template.go b/template/template.go
index 10a9241c7..ae427738e 100644
--- a/template/template.go
+++ b/template/template.go
@@ -22,6 +22,7 @@ import (
 	"net/url"
 	"regexp"
 	"sort"
+	"strconv"
 	"strings"
 	text_template "text/template"
 	"time"
@@ -97,6 +98,17 @@ func query(ctx context.Context, q string, ts time.Time, queryFn QueryFunc) (quer
 	return result, nil
 }
 
+func convertToFloat(i interface{}) (float64, error) {
+	switch v := i.(type) {
+	case float64:
+		return v, nil
+	case string:
+		return strconv.ParseFloat(v, 64)
+	default:
+		return 0, fmt.Errorf("can't convert %T to float", v)
+	}
+}
+
 // Expander executes templates in text or HTML mode with a common set of Prometheus template functions.
 type Expander struct {
 	text    string
@@ -163,9 +175,13 @@ func NewTemplateExpander(
 				sort.Stable(sorter)
 				return v
 			},
-			"humanize": func(v float64) string {
+			"humanize": func(i interface{}) (string, error) {
+				v, err := convertToFloat(i)
+				if err != nil {
+					return "", err
+				}
 				if v == 0 || math.IsNaN(v) || math.IsInf(v, 0) {
-					return fmt.Sprintf("%.4g", v)
+					return fmt.Sprintf("%.4g", v), nil
 				}
 				if math.Abs(v) >= 1 {
 					prefix := ""
@@ -176,7 +192,7 @@ func NewTemplateExpander(
 						prefix = p
 						v /= 1000
 					}
-					return fmt.Sprintf("%.4g%s", v, prefix)
+					return fmt.Sprintf("%.4g%s", v, prefix), nil
 				}
 				prefix := ""
 				for _, p := range []string{"m", "u", "n", "p", "f", "a", "z", "y"} {
@@ -186,11 +202,15 @@ func NewTemplateExpander(
 					prefix = p
 					v *= 1000
 				}
-				return fmt.Sprintf("%.4g%s", v, prefix)
+				return fmt.Sprintf("%.4g%s", v, prefix), nil
 			},
-			"humanize1024": func(v float64) string {
+			"humanize1024": func(i interface{}) (string, error) {
+				v, err := convertToFloat(i)
+				if err != nil {
+					return "", err
+				}
 				if math.Abs(v) <= 1 || math.IsNaN(v) || math.IsInf(v, 0) {
-					return fmt.Sprintf("%.4g", v)
+					return fmt.Sprintf("%.4g", v), nil
 				}
 				prefix := ""
 				for _, p := range []string{"ki", "Mi", "Gi", "Ti", "Pi", "Ei", "Zi", "Yi"} {
@@ -200,14 +220,18 @@ func NewTemplateExpander(
 					prefix = p
 					v /= 1024
 				}
-				return fmt.Sprintf("%.4g%s", v, prefix)
+				return fmt.Sprintf("%.4g%s", v, prefix), nil
 			},
-			"humanizeDuration": func(v float64) string {
+			"humanizeDuration": func(i interface{}) (string, error) {
+				v, err := convertToFloat(i)
+				if err != nil {
+					return "", err
+				}
 				if math.IsNaN(v) || math.IsInf(v, 0) {
-					return fmt.Sprintf("%.4g", v)
+					return fmt.Sprintf("%.4g", v), nil
 				}
 				if v == 0 {
-					return fmt.Sprintf("%.4gs", v)
+					return fmt.Sprintf("%.4gs", v), nil
 				}
 				if math.Abs(v) >= 1 {
 					sign := ""
@@ -221,16 +245,16 @@ func NewTemplateExpander(
 					days := int64(v) / 60 / 60 / 24
 					// For days to minutes, we display seconds as an integer.
 					if days != 0 {
-						return fmt.Sprintf("%s%dd %dh %dm %ds", sign, days, hours, minutes, seconds)
+						return fmt.Sprintf("%s%dd %dh %dm %ds", sign, days, hours, minutes, seconds), nil
 					}
 					if hours != 0 {
-						return fmt.Sprintf("%s%dh %dm %ds", sign, hours, minutes, seconds)
+						return fmt.Sprintf("%s%dh %dm %ds", sign, hours, minutes, seconds), nil
 					}
 					if minutes != 0 {
-						return fmt.Sprintf("%s%dm %ds", sign, minutes, seconds)
+						return fmt.Sprintf("%s%dm %ds", sign, minutes, seconds), nil
 					}
 					// For seconds, we display 4 significant digits.
-					return fmt.Sprintf("%s%.4gs", sign, v)
+					return fmt.Sprintf("%s%.4gs", sign, v), nil
 				}
 				prefix := ""
 				for _, p := range []string{"m", "u", "n", "p", "f", "a", "z", "y"} {
@@ -240,17 +264,25 @@ func NewTemplateExpander(
 					prefix = p
 					v *= 1000
 				}
-				return fmt.Sprintf("%.4g%ss", v, prefix)
+				return fmt.Sprintf("%.4g%ss", v, prefix), nil
 			},
-			"humanizePercentage": func(v float64) string {
-				return fmt.Sprintf("%.4g%%", v*100)
+			"humanizePercentage": func(i interface{}) (string, error) {
+				v, err := convertToFloat(i)
+				if err != nil {
+					return "", err
+				}
+				return fmt.Sprintf("%.4g%%", v*100), nil
 			},
-			"humanizeTimestamp": func(v float64) string {
+			"humanizeTimestamp": func(i interface{}) (string, error) {
+				v, err := convertToFloat(i)
+				if err != nil {
+					return "", err
+				}
 				if math.IsNaN(v) || math.IsInf(v, 0) {
-					return fmt.Sprintf("%.4g", v)
+					return fmt.Sprintf("%.4g", v), nil
 				}
 				t := model.TimeFromUnixNano(int64(v * 1e9)).Time().UTC()
-				return fmt.Sprint(t)
+				return fmt.Sprint(t), nil
 			},
 			"pathPrefix": func() string {
 				return externalURL.Path
diff --git a/template/template_test.go b/template/template_test.go
index a47af9d6b..21583d911 100644
--- a/template/template_test.go
+++ b/template/template_test.go
@@ -179,45 +179,109 @@ func TestTemplateExpansion(t *testing.T) {
 			output: "xa",
 		},
 		{
-			// Humanize.
+			// Humanize - float64.
 			text:   "{{ range . }}{{ humanize . }}:{{ end }}",
 			input:  []float64{0.0, 1.0, 1234567.0, .12},
 			output: "0:1:1.235M:120m:",
 		},
 		{
-			// Humanize1024.
+			// Humanize - string.
+			text:   "{{ range . }}{{ humanize . }}:{{ end }}",
+			input:  []string{"0.0", "1.0", "1234567.0", ".12"},
+			output: "0:1:1.235M:120m:",
+		},
+		{
+			// Humanize - string with error.
+			text:       `{{ humanize "one" }}`,
+			shouldFail: true,
+			errorMsg:   `strconv.ParseFloat: parsing "one": invalid syntax`,
+		},
+		{
+			// Humanize1024 - float64.
 			text:   "{{ range . }}{{ humanize1024 . }}:{{ end }}",
 			input:  []float64{0.0, 1.0, 1048576.0, .12},
 			output: "0:1:1Mi:0.12:",
 		},
 		{
-			// HumanizeDuration - seconds.
+			// Humanize1024 - string.
+			text:   "{{ range . }}{{ humanize1024 . }}:{{ end }}",
+			input:  []string{"0.0", "1.0", "1048576.0", ".12"},
+			output: "0:1:1Mi:0.12:",
+		},
+		{
+			// Humanize1024 - string with error.
+			text:       `{{ humanize1024 "one" }}`,
+			shouldFail: true,
+			errorMsg:   `strconv.ParseFloat: parsing "one": invalid syntax`,
+		},
+		{
+			// HumanizeDuration - seconds - float64.
 			text:   "{{ range . }}{{ humanizeDuration . }}:{{ end }}",
 			input:  []float64{0, 1, 60, 3600, 86400, 86400 + 3600, -(86400*2 + 3600*3 + 60*4 + 5), 899.99},
 			output: "0s:1s:1m 0s:1h 0m 0s:1d 0h 0m 0s:1d 1h 0m 0s:-2d 3h 4m 5s:14m 59s:",
 		},
 		{
-			// HumanizeDuration - subsecond and fractional seconds.
+			// HumanizeDuration - seconds - string.
+			text:   "{{ range . }}{{ humanizeDuration . }}:{{ end }}",
+			input:  []string{"0", "1", "60", "3600", "86400"},
+			output: "0s:1s:1m 0s:1h 0m 0s:1d 0h 0m 0s:",
+		},
+		{
+			// HumanizeDuration - subsecond and fractional seconds - float64.
 			text:   "{{ range . }}{{ humanizeDuration . }}:{{ end }}",
 			input:  []float64{.1, .0001, .12345, 60.1, 60.5, 1.2345, 12.345},
 			output: "100ms:100us:123.5ms:1m 0s:1m 0s:1.234s:12.35s:",
 		},
 		{
-			// Humanize* Inf and NaN.
+			// HumanizeDuration - subsecond and fractional seconds - string.
+			text:   "{{ range . }}{{ humanizeDuration . }}:{{ end }}",
+			input:  []string{".1", ".0001", ".12345", "60.1", "60.5", "1.2345", "12.345"},
+			output: "100ms:100us:123.5ms:1m 0s:1m 0s:1.234s:12.35s:",
+		},
+		{
+			// HumanizeDuration - string with error.
+			text:       `{{ humanizeDuration "one" }}`,
+			shouldFail: true,
+			errorMsg:   `strconv.ParseFloat: parsing "one": invalid syntax`,
+		},
+		{
+			// Humanize* Inf and NaN - float64.
 			text:   "{{ range . }}{{ humanize . }}:{{ humanize1024 . }}:{{ humanizeDuration . }}:{{humanizeTimestamp .}}:{{ end }}",
 			input:  []float64{math.Inf(1), math.Inf(-1), math.NaN()},
 			output: "+Inf:+Inf:+Inf:+Inf:-Inf:-Inf:-Inf:-Inf:NaN:NaN:NaN:NaN:",
 		},
 		{
-			// HumanizePercentage - model.SampleValue input.
+			// Humanize* Inf and NaN - string.
+			text:   "{{ range . }}{{ humanize . }}:{{ humanize1024 . }}:{{ humanizeDuration . }}:{{humanizeTimestamp .}}:{{ end }}",
+			input:  []string{"+Inf", "-Inf", "NaN"},
+			output: "+Inf:+Inf:+Inf:+Inf:-Inf:-Inf:-Inf:-Inf:NaN:NaN:NaN:NaN:",
+		},
+		{
+			// HumanizePercentage - model.SampleValue input - float64.
 			text:   "{{ -0.22222 | humanizePercentage }}:{{ 0.0 | humanizePercentage }}:{{ 0.1234567 | humanizePercentage }}:{{ 1.23456 | humanizePercentage }}",
 			output: "-22.22%:0%:12.35%:123.5%",
 		},
 		{
-			// HumanizeTimestamp - model.SampleValue input.
+			// HumanizePercentage - model.SampleValue input - string.
+			text:   `{{ "-0.22222" | humanizePercentage }}:{{ "0.0" | humanizePercentage }}:{{ "0.1234567" | humanizePercentage }}:{{ "1.23456" | humanizePercentage }}`,
+			output: "-22.22%:0%:12.35%:123.5%",
+		},
+		{
+			// HumanizePercentage - model.SampleValue input - string with error.
+			text:       `{{ "one" | humanizePercentage }}`,
+			shouldFail: true,
+			errorMsg:   `strconv.ParseFloat: parsing "one": invalid syntax`,
+		},
+		{
+			// HumanizeTimestamp - model.SampleValue input - float64.
 			text:   "{{ 1435065584.128 | humanizeTimestamp }}",
 			output: "2015-06-23 13:19:44.128 +0000 UTC",
 		},
+		{
+			// HumanizeTimestamp - model.SampleValue input - string.
+			text:   `{{ "1435065584.128" | humanizeTimestamp }}`,
+			output: "2015-06-23 13:19:44.128 +0000 UTC",
+		},
 		{
 			// Title.
 			text:   "{{ \"aa bb CC\" | title }}",