Canada Post Postage & Parcel Estimator

Introduction: how Canada Post letter and parcel prices are actually set

Canada Post pricing looks simple on a stamp but hides several separate decisions. A letter is first sorted by size: an envelope that stays within 245 mm × 156 mm × 5 mm and 50 g travels as standard Lettermail, while anything larger, thicker, or heavier — up to 380 mm × 270 mm × 20 mm and 500 g — pays the much higher oversize (other) Lettermail tier. Within each tier, the price then jumps in weight bands rather than rising smoothly: a domestic letter costs the same at 31 g as at 50 g, then jumps again at 100 g, 200 g, 300 g, and 400 g. Parcels follow a third logic entirely: prices depend on the origin and destination zone, and bulky boxes are billed by a volumetric equivalent of their actual weight, so a light but oversized box can cost far more than the scale suggests.

This estimator handles all three layers. For letters it carries the current published stamp tables for Lettermail (within Canada), U.S. letter-post, and international letter-post — the prices in force since the January 2025 rate change, when the booklet stamp rose from 99 cents to $1.24 and the single stamp from $1.15 to $1.44, and still current as verified against canadapost.ca in July 2026. You enter the envelope size and weight, and the tool classifies the item as standard or oversize, picks the correct weight band, and shows the exact stamp price along with the reasons for the classification. For parcels, where no single national price list exists, you copy the base price and step price from your own Canada Post quote or rate card, and the calculator applies the volumetric-equivalent rule, chooses the billable weight, and prices the extra weight steps.

In both modes the goal is transparency, not just a dollar figure. The result shows the normalized weight, the size tier and weight band, the dimensional weight when it matters, how much headroom you have before the next price jump, and — when you enter a second packaging option — a side-by-side comparison with the saving spelled out. A price chart draws the full staircase of prices against weight so you can see exactly where your item sits and where the next jump lies.

What the estimator covers and what it leaves to Canada Post

The letter mode answers the everyday question directly: what does it cost to mail this envelope from Canada? It covers the three destinations with published stamp tables — domestic Lettermail, U.S. letter-post, and international letter-post — and both domestic price points for the first weight band, since Permanent stamps bought in booklets, coils, or panes cost $1.24 each while a single stamp costs $1.44. The tool checks the minimum mailable size (140 mm × 90 mm), the standard-size gates (245 mm × 156 mm, 5 mm thick, 50 g), and the oversize gates (380 mm × 270 mm, 20 mm, 500 g), and it explains which specific limit pushed an item into the more expensive tier.

The parcel mode is deliberately different. Canada Post prices parcels by service speed (Regular Parcel, Expedited Parcel, Xpresspost, Priority) and by zone between origin and destination postal codes, and many shippers also have negotiated discounts. Hard-coding one of those tables would make the page wrong for almost everyone, so instead you enter the base band and step pricing from the quote or rate card you already have, and the calculator does the part everyone gets wrong by hand: cubing the box, comparing volumetric and actual weight, and rounding partial steps up the way rate tables do. It does not fetch live parcel prices, look up zones, or validate service eligibility — those stay with Canada Post's own Find a rate tool, which produces the payable amount.

That split makes the page useful in two distinct situations. If you are mailing letters, cards, or documents, the answer is immediate and exact to the published table. If you are shipping merchandise, the page works as a planning and double-checking tool: verify a quote, test whether a smaller box drops the billable weight, or see how close a shipment sits to the next charged step before you add one more item to the order.

Canada Post size limits and the built-in letter rate tables

The size gates are the first thing to check, because they decide which price table applies at all. The limits below apply to domestic Lettermail; U.S. and international letter-post use the same standard and oversize envelope dimensions.

Within each tier, the price comes from a weight band. These are the published stamp prices built into the calculator, in Canadian dollars before tax:

Two details in this table catch people out. First, the domestic booklet-versus-single split only exists in the first band: a 40 g letter costs $1.75 no matter how you buy the postage. Second, the oversize tier is expensive relative to its weight: a 60 g envelope that is 6 mm thick pays $2.61 domestically, exactly the same as a flat 100 g one, because thickness alone pushed it out of the standard tier.

For parcels, the calculator applies Canada Post's cubing rule with the density factor for your service:

Formula and pricing logic used in the estimator

The arithmetic is simple, but keeping it visible explains why the result changes when you alter a weight, dimension, or pricing value. Weights are first normalized to a single unit.

In letter mode, the estimator classifies the item into a tier by testing every limit, then selects the first weight band whose upper bound is at least the item's weight. The price is read directly from the built-in table, so there is no interpolation: the answer is a published stamp price.

In parcel mode, the box is cubed and converted to a volumetric equivalent of actual weight using the density factor for the service.

The billable weight is whichever of the two figures is greater.

Weight above the base band is divided into steps. With the default "round part-steps up" setting, any fraction of a step counts as a whole step, which is how "each additional 0.5 kg or part thereof" tables work.

The estimated postage is the base price plus the charged steps.

Plain-text formula: letter mode: price = built-in table[tier][first band with maxWeight ≥ weight]; parcel mode: estimatedPostage = basePrice + stepPrice × ceil(max(0, max(actualKg, L×W×H÷densityFactor) − baseBandKg) ÷ stepSizeKg).

How to use the estimator for letters, then for parcels

For a letter, leave the mode on the built-in letter rates and choose the destination: Canada, the United States, or international. Measure the envelope's length, width, and thickness — always the fully packed envelope, since a card with a magnet or a folded document changes thickness fast — and weigh it. If the domestic letter is 30 g or less, pick whether you are using a booklet or coil stamp ($1.24) or buying a single stamp ($1.44); for every other band the format makes no difference. Submit, and the result shows the tier, the weight band, the exact stamp price, and how much headroom remains before the next band.

For a parcel, switch the mode to the parcel rate table. Enter the outer dimensions of the packed box, choose the density factor that matches your service — 6,000 for Regular Parcel, 5,000 for Priority, Xpresspost, Expedited, and most U.S. or international parcel services — and copy the pricing values from the quote or chart you are checking: the weight covered by the base price, the base price itself, the size of each additional step, and the price per step. All four values must come from the same service and destination table; mixing a base price from one zone with a step price from another produces a mathematically valid but practically useless estimate.

In either mode you can enter a second packaging option in the comparison fieldset — an envelope trimmed under 5 mm, or a smaller box — and the calculator prices both under the same rules and reports the saving. The copy-estimate button puts a plain-text summary on the clipboard for order notes, and the copy-link button encodes the whole form into a shareable address, so a bookmarked link restores the exact scenario and recalculates on load.

Worked example: a 40 g card and a 1.2 kg parcel

First the letter. A birthday card in its envelope measures 240 mm × 150 mm, is 4 mm thick, and weighs 40 g. Every dimension passes the standard gates (245 mm, 156 mm, 5 mm), so the tier is standard Lettermail. At 40 g it misses the first band (up to 30 g) and lands in the second (over 30 g up to 50 g), so the price is $1.75 — and because that band has a single price, buying stamps in a booklet would not make it cheaper. The result also notes the headroom: 10 g more and the same envelope would leave the standard tier entirely at 50 g, more than doubling the price to the $2.61 oversize band. If the same card were 28 g, the calculator would instead show $1.44 for a single stamp or $1.24 from a booklet.

Now the parcel. A box measures 30 cm × 20 cm × 10 cm and weighs 1.2 kg on the scale, shipping Regular Parcel (density factor 6,000). The cube is 30 × 20 × 10 = 6,000 cm³, so the volumetric equivalent is 6,000 ÷ 6,000 = 1.0 kg. The actual weight of 1.2 kg is higher, so it is the billable weight. Suppose the rate card says $18.50 covers the first 1.0 kg and each additional 0.5 kg or part thereof costs $2.90. The 0.2 kg above the base band is less than one full step, but part-steps round up, so it counts as one step: $18.50 + 1 × $2.90 = $21.40.

Repack that same 1.2 kg into a 40 cm × 30 cm × 20 cm box and the picture flips: the cube is 24,000 cm³, the volumetric equivalent is 4.0 kg, and the billable weight jumps to 4.0 kg even though the scale still reads 1.2 kg. Now there are ceil(3.0 ÷ 0.5) = 6 steps and the estimate is $18.50 + 6 × $2.90 = $35.90. That $14.50 difference is pure packaging, which is exactly what the comparison fieldset is for.

Advanced tools: headroom, packaging comparison, shareable links, and the price chart

Beyond the headline price, the result panel reports band headroom — how many grams or kilograms remain before the next price jump. This is the single most actionable number on the page: if a letter shows 2 g of headroom, weigh it carefully or remove an insert; if a parcel shows most of a step unused, you may be able to add another item to the order for free.

The why-not analysis runs whenever a letter lands in the oversize tier. It lists each standard limit the item failed and by how much — for example, thickness 8 mm is 3 mm over the 5 mm standard limit — and, when the weight alone would have qualified, it prices the hypothetical standard version so you can see exactly what a slimmer envelope would save.

The packaging comparison prices a second size and weight under identical rules and presents both in a table with the saving. In letter mode it re-runs the tier classification, which catches the common case where a slightly smaller or thinner mailer drops from $2.61 to $1.75. In parcel mode it re-runs the cubing, which catches the bulky-box trap in the worked example.

The price chart draws the full staircase of price against weight — the built-in table in letter mode, your entered table in parcel mode — and marks where your item sits on it. Seeing the staircase makes band pricing intuitive: long flat runs are safe zones, and the cliff edges are where a few grams cost dollars. The shareable link captures every input in the page address, so you can keep one bookmark per service you use or send a colleague the exact scenario behind a quote.

Reading the result and troubleshooting surprising estimates

Read the result panel top to bottom: normalized weight first, then the classification (tier and band for letters; actual, volumetric, and billable weight for parcels), then the price, then insights and warnings. If an estimate looks too high, the usual culprits in letter mode are thickness — the 5 mm gate is strict, and padded envelopes fail it easily — or a unit mistake such as entering kilograms as grams. In parcel mode, check the density factor first (5,000 versus 6,000 changes the volumetric weight by 20 percent), then the dimensions, then whether the base band and step values really came from the same table.

If an estimate looks too low, the likely cause is the opposite: a letter you assumed was oversize actually fits standard limits, or a parcel's dimensional weight did not exceed its scale weight. Remember also that every price here excludes tax and optional extras — registration, signature, or additional coverage all cost more at the counter.

Limitations and assumptions

This page is an estimator, not an official Canada Post pricing engine. The letter tables reflect published stamp prices at the time they were last verified (July 2026); Canada Post can change prices, band boundaries, and classification rules, so always confirm before large mailings. The parcel mode prices exactly the table you give it — it does not look up zones, fetch live rates, or apply fuel surcharges, taxes, or negotiated discounts.

The classifier checks size, thickness, and weight, which decide the price tier, but it does not enforce every acceptance rule in the Canada Postal Guide: aspect-ratio requirements, minimum thickness for rigid items, machineability standards, prohibited contents, and packaging rules all still apply in the real mail stream. Items below the 140 mm × 90 mm minimum are flagged as unmailable at letter rates rather than priced.

Finally, the estimator assumes step-priced parcel tables (a base band plus equal increments). Most Canada Post parcel charts and quotes reduce to that shape over the range you care about, but if your table has irregular bands, price each band boundary separately and compare. For a payable checkout amount, the official Find a rate tool or a post office quote is always the source of truth.

Canada Post postage estimates: frequently asked questions