gohugoio/hugo · error

Round operator can't be used with non-float value

Error message

Round operator can't be used with non-float value

What it means

Thrown by math.Round when its single argument cannot be converted to float64 by cast.ToFloat64E. Round rounds half away from zero and needs a numeric input; booleans, nil, structs, slices, and non-numeric strings all fail conversion.

Solutions

1. Cast or default the input: {{ math.Round (float ($v | default 0)) }}.
2. Guard with an if block: {{ if $v }}{{ math.Round $v }}{{ end }}.
3. Fix front matter to use numeric types instead of quoted strings.

Example fix

// before
{{ math.Round .Params.rating }}
// after
{{ with .Params.rating }}{{ math.Round . }}{{ end }}

{{ with $v }}{{ math.Round (float .) }}{{ end }}

When it happens

Trigger: Calling {{ math.Round "foo" }}, {{ math.Round $nilVar }}, or {{ math.Round .Params.someUndefinedKey }}. Also when a front matter field is a date or duration object rather than a number.

Common situations: Rounding a value pulled from params that was authored as a string; passing a time.Time or resource object by mistake; conditional sections where the value is unset on some pages.

Related errors

• Pow operator can't be used with non-float value
• Sqrt operator can't be used with non integer or float value
• can't divide the value by 0
• Ceil operator can't be used with non-float value
• end argument must be integer

AI-assisted analysis of gohugoio/hugo@52c9bd7908 (2026-08-09). Data as JSON: /api/errors/3bed0b9c9eb84709. Report an issue: GitHub.

Appendix: source

Thrown at tpl/math/math.go:225

// Product returns the product of all numbers in inputs. Any slices in inputs are flattened.
func (ns *Namespace) Product(inputs ...any) (product float64, err error) {
	fn := func(x, y float64) float64 {
		return x * y
	}
	return ns.applyOpToScalarsOrSlices("Product", fn, inputs...)
}

// Rand returns, as a float64, a pseudo-random number in the half-open interval [0.0,1.0).
func (ns *Namespace) Rand() float64 {
	return rand.Float64()
}

// Round returns the integer nearest to n, rounding half away from zero.
func (ns *Namespace) Round(n any) (float64, error) {
	xf, err := cast.ToFloat64E(n)
	if err != nil {
		return 0, errors.New("Round operator can't be used with non-float value")
	}

	return _round(xf), nil
}

// Sin returns the sine of the radian argument n.
func (ns *Namespace) Sin(n any) (float64, error) {
	af, err := cast.ToFloat64E(n)
	if err != nil {
		return 0, errors.New("requires a numeric argument")
	}
	return math.Sin(af), nil
}

// Sqrt returns the square root of the number n.
func (ns *Namespace) Sqrt(n any) (float64, error) {
	af, err := cast.ToFloat64E(n)
	if err != nil {

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