Unit Converter

Weight and Mass Converter

Exact mass. Clear conventions.

Convert a mass

Mass units. Clear conventions.

Entry method

Mass value

Decimal, scientific value, fraction or mixed number; a negative value means a signed difference.

From mass unit

To mass unit

Optional container tareSubtract container tare

View results

Precision and report

Display significant figures

Show exact target ratioShow calculation stepsShow every-unit mass table

Decimal/scientific entry allows twenty significant digits, up to eighty characters and written exponents from negative thirty through thirty. Fractions allow one hundred digits per component and two hundred forty characters per field. Conversion factors do not add measurement precision.

Worked examples

Converted mass in kilograms

m_t=68.0388555000\,\mathrm{kg}

Exact named mass factors; rounding affects display only. No local gravity, material density or measurement uncertainty is inferred.

Mass conversion record

Source quantity

m_s=150.000000000\,\mathrm{lb}_{\mathrm{av}}

Original kilograms

m_{\mathrm{gross},kg}=68.0388555000\,\mathrm{kg}

Resulting kilograms

m_{\mathrm{net},kg}=68.0388555000\,\mathrm{kg}

Resulting grams

m_g=68038.8555000\,\mathrm{g}

Source kilogram factor

f_s=\frac{45359237}{100000000}

Target kilogram factor

f_t=1

Source: Avoirdupois pounds. Destination: Kilograms. Factors mean kilograms per one named unit. The exact international avoirdupois pound. SI base unit of mass.

Mass in every supported unit

All twenty-four rows represent the same resulting mass. Avoirdupois and troy ounces, short and long tons, and both hundredweights are separate conventions. Complete copying and CSV retain all rows even when this table is hidden.

Resulting mass in twenty-four named units
Mass convention	Converted quantity
Micrograms	$6.80388555000\times10^{10}\,\mathrm{\mu g}$
Milligrams	$6.80388555000\times10^{7}\,\mathrm{mg}$
Grams	$68038.8555000\,\mathrm{g}$
Kilograms	$68.0388555000\,\mathrm{kg}$
Metric tonnes	$0.0680388555000\,\mathrm{t}$
Grains	$1050000.00000\,\mathrm{gr}$
Avoirdupois ounces	$2400.00000000\,\mathrm{oz}_{\mathrm{av}}$
Avoirdupois pounds	$150.000000000\,\mathrm{lb}_{\mathrm{av}}$
Stones (14 avoirdupois pounds)	$10.7142857143\,\mathrm{st}$
US short tons (2000 pounds)	$0.0750000000000\,\mathrm{ton}_{\mathrm{US,short}}$
Long tons (2240 pounds)	$0.0669642857143\,\mathrm{ton}_{\mathrm{long}}$
Slugs (international-foot FPS)	$4.66214252574\,\mathrm{slug}$
Nanograms	$6.80388555000\times10^{13}\,\mathrm{ng}$
Centigrams	$6803885.55000\,\mathrm{cg}$
Decigrams	$680388.555000\,\mathrm{dg}$
Decagrams	$6803.88555000\,\mathrm{dag}$
Hectograms	$680.388555000\,\mathrm{hg}$
Metric carats (200 milligrams)	$340194.277500\,\mathrm{ct}$
Troy ounces	$2187.50000000\,\mathrm{oz}_{\mathrm{troy}}$
Troy pounds	$182.291666667\,\mathrm{lb}_{\mathrm{troy}}$
Pennyweights	$43750.0000000\,\mathrm{dwt}$
US short hundredweights (100 pounds)	$1.50000000000\,\mathrm{cwt}_{\mathrm{US,short}}$
Long hundredweights (112 pounds)	$1.33928571429\,\mathrm{cwt}_{\mathrm{long}}$
Avoirdupois drams	$38400.0000000\,\mathrm{dr}_{\mathrm{av}}$

Step-by-step mass conversion

1. Identify the source mass convention
Read the full source name. A negative value without tare denotes a signed mass difference, not a negative package.
$m_s=150.000000000\,\mathrm{lb}_{\mathrm{av}}$
2. Normalize the source into kilograms
Multiply by the source unit factor. This is a mass conversion; no local gravity or material density is assumed.
$m_{\mathrm{gross},kg}=m_s f_s=68.0388555000\,\mathrm{kg}$
3. Convert the resulting mass to the target unit
Divide the resulting kilogram mass by the target factor. Every table row describes the same net quantity when tare is enabled.
$m_t=\frac{m_{\mathrm{net},kg}}{f_t}=68.0388555000\,\mathrm{kg}$

What Can You Create?

Compare mass labels without losing their conventions

Packages and net contents

Convert a gross package reading, identify the container mass independently and report net contents in the required unit. Keep both source and tare units alongside the answer so the deduction can be reviewed later.

Everyday and compound readings

Read a source in pounds and ounces, stones and pounds, or one direct metric quantity. The compound method preserves the meaning of the remainder and applies one sign to the complete pair.

Technical and precious-material measures

Compare small SI masses, grains, metric carats, troy measures and the defined FPS slug. Distinct unit names prevent a troy ounce, avoirdupois ounce or fluid ounce from being mistaken for another quantity.

Mass conversion formulas and worked examples

Normalize to kilograms before selecting the target

Let $m_s$ be the entered numerical mass, $f_s$ the kilograms per source unit and $f_t$ the kilograms per destination unit. The source becomes $m_{\mathrm{kg}}=m_s f_s$ , then the target is $m_t=m_{\mathrm{kg}}/f_t$ . The factors carry the unit definitions; they are not measurements of the object. Intermediate quantities remain rational, and only presentation is rounded. For the original example, $150$ avoirdupois pounds become $68.0388555\,\mathrm{kg}$ .

m_t=m_s\frac{f_s}{f_t},\qquad 150\,\mathrm{lb}_{\mathrm{av}}\times\frac{0.45359237\,\mathrm{kg}}{1\,\mathrm{lb}_{\mathrm{av}}}=68.0388555\,\mathrm{kg}

Follow the ounce and grain system

The international avoirdupois pound is exactly $0.45359237\,\mathrm{kg}$ and contains $7000$ grains. Its ounce is one sixteenth of that pound. Troy units use the same grain but group it differently: a troy ounce contains $480$ grains and a troy pound contains $12$ troy ounces. A pennyweight contains $24$ grains. Metric carats are explicitly $200\,\mathrm{mg}$ each and describe gemstone mass, rather than the purity convention used for gold.

1\,\mathrm{oz}_{\mathrm{av}}=28.349523125\,\mathrm g,\qquad 1\,\mathrm{oz}_{\mathrm{troy}}=31.1034768\,\mathrm g

Example: combine a complete compound pair

For $5$ pounds and $8$ ounces, divide the ounces by $16$ before adding to pounds. The result is $5.5\,\mathrm{lb}_{\mathrm{av}}$ , which converts to $2.494758035\,\mathrm{kg}$ . In the stone method the divisor is $14$ : $10$ stones and $10$ pounds is $150\,\mathrm{lb}_{\mathrm{av}}$ . The major field must be whole, and the minor field must remain below its divisor. With a negative pair sign, negate the entire combined mass rather than only its remainder.

m_s=\sigma\left(a+\frac bD\right),\qquad 5+\frac8{16}=5.5,\qquad 10\times14+10=150

Example: subtract tare using independent units

Suppose a package and its contents have a gross mass of $12.5\,\mathrm{kg}$ and the empty container has a mass of $500\,\mathrm g$ . First convert the container to $0.5\,\mathrm{kg}$ , then subtract to obtain $12\,\mathrm{kg}$ of contents. Subtracting the written numbers before normalizing their units would be incorrect. The report shows the gross and container masses separately, while every conversion row uses the net contents. A container exceeding the gross entry signals inconsistent inputs.

m_{\mathrm{net},kg}=m_{\mathrm{gross},kg}-m_{\mathrm{tare},kg}=12.5\,\mathrm{kg}-0.5\,\mathrm{kg}=12\,\mathrm{kg}

Keep mass, force and volume separate

The mass of an object and its gravitational weight are different quantities. Weight as a force follows $W=mg$ and requires a stated acceleration. Fluid ounces and liters describe volume, so a mass-to-volume calculation instead needs a material density, through $V=m/\rho$ . Neither gravity nor density is inferred here. For the slug factor only, the conventional standard acceleration $9.80665\,\mathrm{m/s^2}$ and international foot $0.3048\,\mathrm m$ supply a defined unit relationship, rather than a location-specific prediction.

Why Users Love This Tool

Keep every mass calculation inspectable

Check the convention first

Troy and avoirdupois measures have explicit labels and independent factors.
Short and long tons and hundredweights remain separate from metric tonnes.
The slug factor is derived before rounding, rather than stored as an approximate decimal.

Preserve the complete calculation

Inspect gross, normalized tare and net quantities together.
Store source syntax and exact certificates with every converted unit.
Reject inconsistent physical tare inputs and out-of-range compound remainders.

Perfect For

Useful for learning, parcels and mixed measurement documents

Students and teachers

Trace the kilogram route, compare troy and ordinary ounces, and explain why a mass conversion does not require local gravity. Exact factors make the arithmetic reproducible while the guide keeps measurement uncertainty separate.

Inventory and parcel users

Convert a stated gross quantity, normalize the empty-container reading and compare net contents across unit systems. The result is a numerical calculation, so preserve the original scale reading and source convention when preparing an operational record.

Readers of compound labels

Enter pounds with ounces or stones with pounds directly instead of treating the remainder as decimal digits. Identify the system on the original label before choosing an ounce, ton or hundredweight in a specification.

How It Works

How it works in three quick steps.

Read the mass convention and enter the source

Choose direct mass entry or a compound pounds-and-ounces or stones-and-pounds pair. For a direct source, identify the full unit name, including avoirdupois, troy, short ton or long ton. Enter a decimal, scientific value, simple fraction or proper mixed number. A compound pair uses nonnegative whole major units and a smaller remaining quantity under one shared sign.

Choose the target and any container deduction

Select a destination unit. If the entry includes a container, enable tare and enter its nonnegative mass with an independent unit. The gross source must be nonnegative and at least as large as the normalized tare. Review original kilograms, tare kilograms and net contents separately. Disable tare for signed mass differences.

Inspect the factors and save the mass record

Choose three through twelve significant figures for display, then inspect the exact target ratio, unit table and generated working. Copy the complete summary or LaTeX, download the full CSV, share validated settings or print the visible report. Exact swapping adopts the resulting net quantity and disables tare so the container is not deducted a second time.

Download & Print

Save the mass result with the information needed to reproduce it

Copy text or mathematical working

Copy the complete context and plain-text record or the generated LaTeX steps. Compound signs and tare units are retained. If clipboard access fails, the tool announces the failure and offers CSV as a complete alternative.

Download the full unit table

CSV retains hidden rows, exact signed numerators and denominators, kilogram factors and active inputs. Import large exact certificates as text in a spreadsheet to avoid losing digits. Display precision changes the presentation, not these exact numerical fields.

Print or save a PDF

Choose the report sections, select Print / Save PDF and inspect the browser preview. Editing controls and the supporting guide are excluded. Very long ratios receive a compact-print explanation; their complete exact digits remain in the copied record and CSV.

FAQ

Frequently Asked Questions

Does this converter measure mass or gravitational weight?

It converts mass, even though everyday labels often call the quantity weight. Kilograms, grams, avoirdupois pounds and slugs are mass units. Gravitational weight is a force described by

W=mg

and expressed in newtons in SI. Changing location does not change the defined pound-to-kilogram relationship. Use a force calculation with a stated gravitational acceleration when that is the quantity you actually need.

Are avoirdupois ounces, troy ounces and fluid ounces interchangeable?

No. The ordinary mass ounce here is one sixteenth of an avoirdupois pound, while the troy ounce is

480

grains. Consequently

1\,\mathrm{oz}_{\mathrm{av}}=28.349523125\,\mathrm g

and

1\,\mathrm{oz}_{\mathrm{troy}}=31.1034768\,\mathrm g

. A fluid ounce measures volume and is not a choice on this page. Read the original label carefully; converting between a mass and a volume additionally requires the relevant material density.

Which ton or hundredweight should I choose?

Choose the convention explicitly named in the source document. A US short ton is

2000

avoirdupois pounds, a long ton is

2240

pounds, and a metric tonne is

1000\,\mathrm{kg}

. The short hundredweight contains

100

pounds and the long hundredweight contains

112

pounds. An unlabeled ton or hundredweight can therefore be ambiguous. The calculator keeps these entries separate and does not infer a trade convention from your location.

How do I enter pounds with ounces or stones with pounds?

Select the corresponding compound entry method. Supply a nonnegative whole major quantity and a remaining minor quantity below the next major unit: below

16

ounces for pounds-and-ounces, or below

14

pounds for stones-and-pounds. Fractions are permitted in the remaining quantity. Choose one sign for the complete pair; do not put another sign on the remainder. An out-of-range remainder is rejected rather than silently carried into the major field.

How does container tare work when the units differ?

Enable the tare option only when the entered source is the gross mass of contents plus container. The converter normalizes both the gross entry and independently selected container unit to kilograms before applying

m_{\mathrm{net}}=m_{\mathrm{gross}}-m_{\mathrm{tare}}

. Equal masses give zero contents. A negative container, negative gross entry or container heavier than the gross mass is rejected. Unit swapping uses the resulting net mass and disables tare to avoid deducting it twice.

Why is the slug factor not a short rounded decimal?

The slug is an FPS mass unit, distinct from the pound mass. This page derives it from the international avoirdupois pound, international foot and standard gravity rather than treating a rounded table value as exact. The adopted relationship is

1\,\mathrm{slug}=(0.45359237\times9.80665/0.3048)\,\mathrm{kg}

. Its displayed decimal depends on the selected significant figures. The standard-gravity definition of this unit does not mean your local gravitational acceleration was measured or inferred.

Do exact fractions and extra significant figures improve a scale measurement?

They preserve the entered numerical model and its conversion factors, but they cannot add information to a measurement. Exact rational arithmetic avoids intermediate binary floating-point rounding. Three through twelve significant figures control the displayed values; repeating decimals use an approximation sign. A fraction certificate may be exact for an entered value whose physical accuracy is limited by a scale, sampling method or original rounded label. Keep that original context with the exported record.

What do CSV, sharing, copying and PDF preserve?

Complete copied text and CSV retain every mass-unit row, exact signed numerators and denominators, active source conventions, compound sign, container settings and calculation steps, even if those report sections are hidden on screen. Share links encode validated active inputs and display preferences. The print action saves the visible mathematical report through the browser print dialog. Exceptionally long exact ratios receive a compact-print notice, while CSV and copied text retain their full digits.

Related quantity tools

Continue with volume, density or force

Volume Converter

Compare liters and fluid measures when the source describes a capacity.

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Density Calculator

Relate a known mass to volume using the appropriate density model.

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Force Converter

Convert force units when the quantity is gravitational weight or another force.

Try it

About This Tool

About this Weight and Mass Converter

The Toolarithm Weight and Mass Converter translates explicitly named mass quantities through kilograms while retaining the context of the original entry. Everyday language often describes a scale label as weight, but the numerical relationships here are mass relationships. The original pounds-to-kilograms example remains available alongside the previous mass-unit identifiers. The expanded catalog adds intermediate SI prefixes, gemstone carats, troy measures, pennyweights, both hundredweights and a clearly named avoirdupois dram. The slug uses a derived international-foot FPS definition instead of promoting a rounded lookup-table decimal into an exact factor.

Single-value entry supports decimals, scientific syntax, simple fractions and proper mixed numbers. The two compound methods treat pounds with ounces and stones with pounds as pairs under a shared sign. Major quantities must be whole and nonnegative; minor remainders must stay below the next major unit. This prevents a familiar label such as pounds and ounces from being misread as a decimal. Signed differences are useful numerical quantities and remain available when physical container subtraction is disabled. They are not described as negative objects or packages.

Optional tare is an independently entered container mass. The converter normalizes gross and container quantities separately and subtracts the latter once, preserving both original kilograms and resulting contents in the report. It rejects a container heavier than the gross mass instead of fabricating a usable package result. Exact arithmetic protects the entered numerical model, while the selected significant figures govern its presentation. Copying, sharing, CSV and print offer different ways to retain that model for later inspection. The page does not infer material density, local gravitational acceleration, gemstone purity, medical dosage or legal labeling requirements from a mass value.

Editorial Transparency

Who maintains this page

Ownership and review

Written and maintained by the Toolarithm editorial team. No review date is shown without a maintained editorial record. No independent professional review is claimed.

Methodology

Conversion factors are normalized to canonical units and checked in both directions. Exact definitions and offset formulas are preferred over rounded lookup values.

Read the editorial methodology

Dates and sources

Review dates change only after a substantive method or content check.

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