An airfreight rate sheet may show M, N, +45, +100, +300 and +500 columns with lower per-kilogram rates at higher weights. A common mistake is to multiply the gross weight by the nearest column or assume that a shipment below 100 kg can never use the +100 rate. In practice, the chargeable weight must be established first, then the total freight at the current bracket should be compared with the threshold weight of the next bracket. A 92 kg shipment can therefore cost less when rated at 100 kg under the +100 rate than when rated at 92 kg under +45. This article explains each column, chargeable-weight calculation, break-even points and the surcharges excluded from the base rate.

QUICK FACTS

“+” means a threshold

+45 means a per-kg rate from the 45 kg threshold, subject to the tariff; it does not mean adding 45 kg.

Calculate chargeable weight first

Compare actual gross weight with volumetric weight, use the higher value and then apply the stated rounding rule.

Compare totals, not only rates

A lower rate per kg does not automatically produce a lower total freight charge.

Buying up may be cheaper

If the next break’s minimum-weight total is lower, that bracket may be used where the tariff permits.

Check surcharges separately

Fuel, security, screening, handling, trucking and minimum charges may use a different calculation basis.

SCOPE OF APPLICATION

This article applies mainly to general-cargo airfreight quotations stated as a currency amount per chargeable kilogram. M, N, +45, +100, +300 and +500 are common commercial tariff notations; not every airline, route or product offers every break.

Dangerous goods, valuables, live animals, pharmaceuticals, temperature-controlled, oversized, unusually dense cargo and spot bookings may be subject to separate rates, minimums, ULD/pallet pricing and surcharges. Final pricing also depends on actual dimensions at acceptance, service type, flight and applicable charges.

Principle: the breaks are tariff thresholds, not statutory rules or a universal market rate sheet.

TERMS EXPLAINED

Term	Meaning	Role when reading the rate
M – Minimum Charge	The minimum weight/volume charge per shipment or AWB under the tariff.	If the per-kg calculation is below M, the weight charge may be raised to M; surcharges may have separate minimums.
N – Normal Rate	The normal per-kg rate, commonly below the first weight break.	Read it together with the minimum, rounding and commodity conditions.
+45 / +100 / +300 / +500	Quantity-rate thresholds; on an AWB, a quantity rate is commonly shown as Rate Class Q.	Used to identify the current bracket and compare the next one.
Actual Gross Weight	Physical weight including cargo, packaging, pallets and dunnage.	One input for chargeable weight.
Volumetric Weight	A weight equivalent calculated from occupied volume.	Commonly cm³ divided by 6,000 for air cargo, subject to tariff.
Chargeable Weight – CW	Usually the higher of gross and volumetric weight.	The starting point for selecting the weight break.
Higher Weight Break	A rating technique that applies the next quantity-rate tier by charging at least its threshold weight, where permitted by the tariff.	Optimizes base freight without changing actual gross weight or dimensions.
Base Freight	Air carriage charge before other surcharges and services.	It is not the total door-to-door airfreight cost.

HOW TO READ EACH RATE-SHEET COLUMN

Column	Correct interpretation	What to verify	Common error
M	Minimum weight/volume charge for one shipment/AWB.	Currency, route and whether surcharges have their own minimums.	Treating M as a per-kg rate or assuming it includes every surcharge.
N	Normal rate for the band below the first break, often below 45 kg.	Minimum, rounding and commodity conditions.	Assuming N always applies to every shipment below 45 kg.
+45	Per-kg rate from the 45 kg break.	Whether buying up to 45 kg is allowed.	Using 43 × +45 without comparing N with 45 × +45.
+100	Per-kg rate from 100 kg.	Compare CW × current rate with 100 × +100 rate.	Assuming a 92 kg shipment cannot use +100.
+300	Per-kg rate from 300 kg.	Aircraft, piece dimensions and acceptance.	Ignoring oversize or pallet-position constraints.
+500	Per-kg rate from 500 kg.	Capacity, allotment, dense-cargo and spot conditions.	Assuming the rate guarantees space.

Read the row for the correct origin, destination, airline/product, commodity and validity. Direct, transit, priority and allotment products may have different rates on the same route.

CALCULATE CHARGEABLE WEIGHT BEFORE SELECTING A BREAK

Volumetric Weight (kg) = Sum of (Length × Width × Height (cm) × Number of Pieces) ÷ 6,000

Chargeable Weight = Higher of Actual Gross Weight and Volumetric Weight, after the tariff’s rounding rule.

Step	Data	Treatment	Control point
1. Gross weight	Cargo, packaging, pallets and dunnage.	Sum all pieces using acceptance data.	Do not use invoice net weight.
2. Dimensions	Maximum external L/W/H of every piece.	Calculate each piece then total the volume.	Include pallets and projections; confirm dimension rounding.
3. Volume conversion	Total cm³ and divisor.	Commonly divide by 6,000 for air cargo.	A contract or product may use another rule.
4. Select CW	Gross versus volumetric.	Use the higher value.	Acceptance CW may differ from booking data.
5. Rounding	Carrier/agent/AWB rule.	Round exactly as stated.	Do not invent a 0.5 kg or 1 kg rule.

Example: four pieces each measuring 80 × 60 × 50 cm, with a total gross weight of 120 kg. Volumetric Weight = 4 × 80 × 60 × 50 ÷ 6,000 = 160 kg. The preliminary CW is 160 kg, not 120 kg.

SELECTING A WEIGHT BREAK AND CALCULATING THE BREAK-EVEN POINT

After establishing CW, first use the bracket already reached. Then compare it with the next bracket to determine whether buying up reduces the base freight.

Current-bracket Freight = CW × Current Rate

Next-break Freight = Next Threshold Weight × Next Rate

Break-even Weight = Next Threshold Weight × Next Rate ÷ Current Rate

Comparison	CW below break-even	CW at/above break-even	Condition
N vs +45	Keep N, subject to M.	The shipment may be rated at 45 kg under +45.	The tariff permits a higher break and the total is lower.
+45 vs +100	Use CW × +45.	The shipment may be rated at 100 kg under +100.	Physical gross/dimensions remain accurate.
+100 vs +300	Use CW × +100.	The shipment may be rated at 300 kg under +300.	Check whether each surcharge uses gross weight, chargeable weight, shipment or its own minimum.
+300 vs +500	Use CW × +300.	The shipment may be rated at 500 kg under +500.	Capacity, dimensions and booking acceptance still apply.

Buying up is a freight-rating technique, not permission to falsify gross weight or dimensions. Quantity rates are commonly shown as Rate Class Q on the AWB; chargeable weight and rate/charge entries must follow the applicable rating rules and carrier or agent instructions.

INTEGRATED EXAMPLES FROM +45 TO +500

Assume this illustrative base tariff: M = USD 80/shipment; N = USD 5.20/kg; +45 = 4.60; +100 = 4.10; +300 = 3.55; +500 = 3.20. These figures demonstrate the method and are not market rates.

Actual CW	Current-bracket option	Buy-up option	Optimized freight	Reason
38 kg	38 × 5.20 = USD 197.60	45 × 4.60 = USD 207.00	USD 197.60 at N	38 kg is below the N/+45 break-even of 39.81 kg.
43 kg	43 × 5.20 = USD 223.60	45 × 4.60 = USD 207.00	USD 207.00 rated at 45 kg	Buying up saves USD 16.60 if allowed.
92 kg	92 × 4.60 = USD 423.20	100 × 4.10 = USD 410.00	USD 410.00 rated at 100 kg	The +45/+100 break-even is 89.13 kg.
275 kg	275 × 4.10 = USD 1,127.50	300 × 3.55 = USD 1,065.00	USD 1,065.00 rated at 300 kg	The +100/+300 break-even is 259.76 kg.
470 kg	470 × 3.55 = USD 1,668.50	500 × 3.20 = USD 1,600.00	USD 1,600.00 rated at 500 kg	The +300/+500 break-even is 450.70 kg.
18 kg	18 × 5.20 = USD 93.60	Compare with M = USD 80	USD 93.60 if M is only the floor	M does not replace a higher kg calculation.

Not the final invoice: add fuel, security, screening, terminal/handling, AWB, pickup/delivery and special-cargo charges according to the quotation scope.

DOCUMENTS AND DATA TO CHECK

Data/document	Provider	Use	Fields to lock
Rate sheet/quotation	Airline or forwarder	Select route and break.	Origin, destination, airline, product, currency, validity, M/N/breaks.
Packing List	Shipper/supplier	Estimate gross and dimensions.	Pieces, gross per piece, outer dimensions and pallets.
Dimension confirmation	Warehouse/factory/packer	Finalize volumetric weight.	Post-packing dimensions, projections and stackability.
Booking confirmation	Airline/forwarder	Confirm flight and space.	Flight, routing, product, booked CW, commodity and handling.
Rate conditions	Airline/forwarder	Check buying up and minimums.	Rounding, Rate Class Q, higher weight break, dense cargo and cancellation/no-show.
Surcharge sheet	Airline/forwarder/terminal	Build the full invoice.	Fuel/security basis, minimum, handling, AWB and screening.
Acceptance data	Terminal/airline	Finalize pricing.	Actual gross, measured dimensions, accepted pieces and final CW.
AWB and invoice/debit note	Carrier/agent	Reconcile.	Gross weight, chargeable weight, Rate Class M/N/Q, rate/charge, total and other charges.

PROCESS / HOW TO APPLY

Step	Action	Output	Control
1. Collect cargo data	Obtain post-packing gross, dimensions, pieces and commodity.	Initial RFQ dataset.	Do not use unpacked product dimensions.
2. Calculate volume	Calculate every piece and total it.	Preliminary volumetric weight.	Keep the calculation for acceptance reconciliation.
3. Establish CW	Use the higher weight and apply rounding.	CW for reading the tariff.	Record divisor and rounding.
4. Select current bracket	Place CW into N/+45/+100/+300/+500.	Current freight total.	Check M.
5. Compare next break	Calculate threshold × next rate or use the break-even formula.	Optimized base freight.	Buy up only where permitted.
6. Add surcharges	Separate fuel, security, handling, AWB and delivery.	Full quotation scope.	Do not assume the same weight basis.
7. Confirm capacity	Submit dimensions, commodity, routing and flight date.	Confirmed booking/space.	A rate is not a space guarantee.
8. Reconcile acceptance	Compare actual measurements, AWB and invoice.	Final CW and variance.	Identify dimension, rounding, break and surcharge differences.

RISKS AND COMMON ERRORS

Error	Cause	Impact	Control
Using gross instead of CW	Volume was not calculated.	Underbudgeting and acceptance uplift.	Calculate both gross and volumetric.
Reading +100 as “add 100 kg”	Misunderstood notation.	Completely wrong formula.	Treat it as a threshold.
Selecting the lowest rate/kg immediately	No total-cost comparison.	The buy-up can be more expensive.	Compare current and next-break totals.
Ignoring M	Only N × small weight was calculated.	Actual freight exceeds estimate.	Read minimum conditions.
Using +100 for 92 kg but multiplying by 92	Misunderstood buy-up.	Understated tariff charge.	A +100 buy-up normally rates at at least 100 kg.
Applying every surcharge to the buy-up weight	Surcharge terms were not checked.	Wrong invoice total.	Confirm gross-weight, chargeable-weight, per-shipment and minimum rules for each charge.
Using booking dimensions after acceptance	Packaging changed or was remeasured.	Final CW increases.	Confirm post-packing dimensions and allow variance.
Ignoring oversize/non-stackable	Only kg was considered.	Rate change, rejection or position charge.	Submit dimensions and stackability before booking.
Comparing different scopes	One quote includes fuel/security and another does not.	Wrong supplier selection.	Normalize base, surcharge, handling, trucking and validity.

OPERATIONAL BASIS AND OFFICIAL SOURCES

Source	Organization	Point verified	Application
Air Cargo Tariffs and Rules	IATA	Air pricing depends on weight and volume; general guidance uses cm³/6,000 and the higher weight.	Principle only; actual rates come from the effective tariff.
Cargo Agent’s Handbook – Resolution 801, Edition 47	IATA	Confirms Rate Class M for minimum charge, N for normal rate and Q for quantity rate; pivot weight is an ULD-rating concept.	Use it to read AWB rate classes correctly and avoid equating pivot weight with a higher weight break.
Click & Ship User Guide – updated 2 Jul 2026	Cathay Cargo	Final prices depend on actual size, volume, weight, service and surcharges; the summary separates freightage, fuel, security and truck cost.	Confirms base freight is not the total price.
General Terms and Conditions of Carriage	Lufthansa Cargo	Freight depends on the higher weight/volume and many services or surcharges are outside the base freight.	Check carrier scope and tariff conditions.

Sources checked on 17 July 2026. Weight breaks, rates, rounding, minimums and surcharge rules must be confirmed on the shipment’s effective quotation/tariff.

FAQ

Can a 44 kg shipment use the +45 rate?

Possibly, where the tariff permits a higher break. Compare 44 × N with 45 × +45 and apply the valid lower total.

Must a 99 kg shipment always use +45?

No. Compare 99 × +45 with 100 × +100; buying up may be cheaper.

Is chargeable weight always rounded to a whole kilogram?

There is no universal rounding rule. Follow the quotation, booking system and AWB conditions.

Is the airfreight divisor always 6,000?

6,000 cm³/kg is a common general rule, but a contract, product or provider may specify otherwise.

Are fuel and security charged on the buy-up weight?

Not automatically. Each surcharge may use gross weight, chargeable weight, a per-shipment basis or its own minimum.

Does a +500 rate guarantee acceptance of 500 kg?

No. Space, aircraft, dimensions, commodity and flight date still require confirmation.

Should gross weight be changed to 100 kg when buying +100?

No. Physical gross and dimensions must remain accurate. The 100 kg figure is a tariff rating mechanism.

APPLICATION NOTE: Before booking, require the quotation to state M/N/breaks, divisor, rounding, higher-break rule, surcharge basis, minimum, validity, routing, commodity and included/excluded scope. Numerical examples are illustrative only.

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